Method and apparatus for random access procedure and broadcast prioritization

Abstract

Disclosed are methods and apparatus for random access procedures and broadcast prioritization. Certain aspects of the present disclosure relate generally to wireless communications, and more particularly to random access procedures and / or broadcast transmission prioritization in machine type communication (MTC) devices and enhanced MTC (eMTC). An example method generally includes: determining a plurality of subframes in which the UE may transmit a bundled random access channel (RACH) message to a base station (BS); determining at least one narrowband region within the subframes for transmitting the bundled RACH message; determining a bundle size for the bundled RACH message, the bundle size indicating the number of the plurality of subframes in which the bundled RACH message is transmitted; and transmitting the bundled RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

Description

[0001] This application is a divisional application of a Chinese patent application filed on January 29, 2016, with application number 201680007478.4 (international application number PCT / US2016 / 015523), and invention name “Random Access Procedure and Broadcast Priority Differentiation for Machine Type Communication (MTC)”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 110,164, filed on January 30, 2015, U.S. Provisional Application No. 62 / 165,823, filed on May 22, 2015, and U.S. Patent Application No. 15 / 009,804, filed on January 28, 2016, all of which are assigned to the assignee of this application and are hereby expressly incorporated herein by reference. Technical Field

[0004] Certain aspects of the present disclosure relate generally to wireless communications, and more particularly to random access procedures and / or broadcast transmission prioritization in machine type communications (MTC) and enhanced or evolved MTC (eMTC). Background Art

[0005] Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, etc. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, third generation partnership project (3GPP) long term evolution (LTE) (including advanced LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.

[0006] In general, a wireless multiple access communication system can support the communication of multiple wireless terminals simultaneously. Each terminal communicates with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from the base station to the terminal, while the reverse link (or uplink) refers to the communication link from the terminal to the base station. Such communication links can be established via single-input single-output, multiple-input single-output, or multiple-input multiple-output (MIMO) systems.

[0007] A wireless communication network may include several base stations that can support communications for several wireless devices. The wireless devices may include user equipment (UE). Some UEs may be considered machine type communication (MTC) UEs, which may include remote devices that can communicate with a base station, another remote device, or some other entity. Machine type communication (MTC) may refer to communications involving at least one remote device at at least one end of the communication, and may include a form of data communication involving one or more entities that do not necessarily require human-computer interaction. MTC UEs may include UEs capable of MTC communications with an MTC server and / or other MTC devices via, for example, a public land mobile network (PLMN). Summary of the invention

[0008] The systems, methods, and devices of the present disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of the present disclosure as expressed in the appended claims, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled "Detailed Description," it will be understood how the features of the present disclosure provide advantages including improved communication between access points and stations in a wireless network.

[0009] Provided herein are techniques and apparatus for random access procedures and / or broadcast transmission prioritization in MTC and enhanced MTC (eMTC). MTC / eMTC devices include devices such as sensors, meters, monitors, location tags, remote-controlled aircraft, trackers, robots / robotic devices, and the like. MTC / eMTC devices may be implemented as Internet of Everything (IoE) devices or Internet of Things (IoT) devices (e.g., narrowband IoT (NB-IoT) devices). In order to enhance coverage of certain devices (such as MTC devices), "bundling" may be utilized, in which certain transmissions are sent as transmission bundles (e.g., transmitting the same information over multiple subframes). Certain aspects of the present disclosure relate to determining resources and / or bundle sizes for messages exchanged during a random access procedure.

[0010] Certain aspects of the present disclosure provide a method for wireless communication by a user equipment (UE). The method generally includes: determining a plurality of subframes in which the UE may transmit a bundled random access channel (RACH) message to a base station (BS); determining at least one narrowband region within the subframes for transmitting the RACH message; and determining a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted. The method also includes transmitting the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

[0011] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes: a device for determining a plurality of subframes in which the apparatus can transmit a bundled RACH message to a BS; a device for determining at least one narrowband region within the subframes for transmitting the RACH message; and a device for determining a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted. The apparatus also includes a device for transmitting the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

[0012] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes at least one processor configured to: determine a plurality of subframes in which the apparatus can transmit a bundled RACH message to a BS; determine at least one narrowband region within the subframes for transmitting the RACH message; and determine a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted. The apparatus may also include a transmitter configured to transmit the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size. The apparatus may further include a memory coupled to the at least one processor.

[0013] Certain aspects of the present disclosure provide a computer-readable medium having computer-executable code stored thereon. The computer-executable code generally includes code for the following operations: determining a plurality of subframes in which a UE can transmit a bundled RACH message to a BS; determining at least one narrowband region within the subframes for transmitting the RACH message; and determining a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted. The computer-executable code also includes code for transmitting the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

[0014] Certain aspects of the present disclosure provide a method for wireless communication by a BS. The method generally includes: determining a plurality of subframes in which a UE may transmit a bundled RACH message to the BS; determining at least one narrowband region within the subframes for receiving the RACH message; and determining a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted by the UE. The method also includes receiving the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

[0015] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes: a device for determining a plurality of subframes in which a UE may transmit a bundled RACH message to the apparatus; a device for determining at least one narrowband region within the subframes for receiving RACH messages; and a device for determining a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted by the UE. The apparatus also includes a device for receiving the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

[0016] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes at least one processor configured to: determine a plurality of subframes in which a UE may transmit a bundled RACH message to the apparatus; determine at least one narrowband region within the subframes for receiving RACH messages; and determine a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted by the UE. The apparatus may also include a receiver configured to receive the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size. The apparatus may further include a memory coupled to the at least one processor.

[0017] Certain aspects of the present disclosure provide a computer-readable medium having computer-executable code stored thereon. The computer-executable code generally includes code for the following operations: determining a plurality of subframes in which a UE can transmit a bundled RACH message to a BS; determining at least one narrowband region within the subframes for receiving RACH messages; and determining a bundle size for the RACH message. The bundle size indicates the number of the plurality of subframes in which the RACH message is transmitted by the UE. The computer-executable code also includes code for receiving the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundle size.

[0018] Certain aspects of the present disclosure provide a method for wireless communication. The method generally includes: selecting a RACH preamble from a set of RACH preambles; transmitting a physical RACH (PRACH) message including the RACH preamble; determining RAR resources for receiving a random access response (RAR) message based at least in part on the RACH preamble; and receiving the RAR message on the RAR resources.

[0019] Certain aspects of the present disclosure provide a method for wireless communications. The method generally includes receiving a PRACH message including a RACH preamble; and selecting a RAR resource for transmitting a RAR message based at least in part on the RACH preamble.

[0020] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes: means for selecting a RACH preamble from a set of RACH preambles; means for transmitting a PRACH message including the RACH preamble; means for determining RAR resources for receiving a RAR message based at least in part on the RACH preamble; and means for receiving the RAR message on the RAR resources.

[0021] Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus generally includes: means for receiving a PRACH message including a RACH preamble; and means for selecting a RAR resource for transmitting a RAR message based at least in part on the RACH preamble.

[0022] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus includes at least one processor, a memory coupled to the at least one processor, a transmitter, and a receiver. The at least one processor is configured to: select a RACH preamble from a set of RACH preambles; transmit a PRACH message including the RACH preamble via a transmitter; determine a RAR resource for receiving a RAR message based at least in part on the RACH preamble; and receive the RAR message on the RAR resources via a receiver.

[0023] Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus includes at least one processor, a memory coupled to the at least one processor, and a receiver. The receiver is configured to receive a PRACH message including a RACH preamble. The at least one processor is configured to select a RAR resource for transmitting a RAR message based at least in part on the RACH preamble.

[0024] Certain aspects of the present disclosure provide a method for wireless communication. The method generally includes: selecting a bundle size for a PRACH message; determining a PRACH resource for PRACH message transmission based at least in part on the bundle size; and transmitting the PRACH message using the PRACH resource.

[0025] In some aspects, the PRACH resource may include a narrowband frequency region of a carrier bandwidth. Determining the PRACH resource may include determining the narrowband frequency region from a set of narrowband frequency regions based at least in part on a bundle size. The method may also include identifying the set of narrowband frequency regions from a system information broadcast message. The method may further include selecting a RACH preamble, wherein the PRACH resource is determined independently of the RACH preamble, and wherein the PRACH message includes the RACH preamble.

[0026] In some aspects, the PRACH resource may include a RACH preamble. Determining the PRACH resource may include determining the RACH preamble from a set of RACH preambles based at least in part on the bundle size. The method may also include selecting a narrowband frequency region in a carrier bandwidth for PRACH message transmission independent of the RACH preamble. In some cases, determining the RACH preamble may include randomly selecting a RACH preamble from the set of RACH preambles.

[0027] The method may also include determining a start transmission time for the PRACH message based at least in part on the bundle size.Determining the start transmission time may include randomly selecting the start transmission time from a set of start transmission times.

[0028] The method may further include selecting a transmit power for the PRACH message.The PRACH resource may be determined based at least in part on the selected transmit power.

[0029] Certain aspects of the present disclosure provide a method for wireless communication. The method generally includes: receiving a PRACH message transmitted using a first PRACH resource; and determining a second PRACH resource for the PRACH message based at least in part on the first PRACH resource for the PRACH message. The first or second PRACH message may include at least one of a RACH preamble, a PRACH message bundle size, a narrowband frequency resource, or a start transmission time.

[0030] Numerous other aspects are provided, including methods, apparatus, systems, computer program products, computer readable media, and processing systems. To achieve the foregoing and related purposes, one or more aspects include features fully described below and particularly pointed out in the appended claims. The following description and accompanying drawings set forth in detail certain illustrative features of the one or more aspects. However, these features are merely indicative of several of the various ways in which the principles of the various aspects may be employed, and the present description is intended to cover all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to understand in detail the manner in which the above-stated features of the present disclosure are used, a more particular description of the content briefly summarized above may be made with reference to various aspects, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only certain typical aspects of the present disclosure and are not to be considered limiting of its scope, as the description may admit to other equally effective aspects.

[0032] Figure 1 is a block diagram conceptually illustrating an example wireless communication network in accordance with certain aspects of the present disclosure.

[0033] Figure 2is a block diagram conceptually illustrating an example of an evolved Node B (eNB) and a user equipment (UE) in communication in a wireless communication network in accordance with certain aspects of the present disclosure.

[0034] Figure 3 is a block diagram conceptually illustrating an example frame structure of a particular radio access technology (RAT) for use in a wireless communication network, in accordance with certain aspects of the present disclosure.

[0035] Figure 4 Illustrated are example subframe formats for the downlink with a normal cyclic prefix in accordance with certain aspects of the present disclosure.

[0036] Figure 5A and 5B An example of machine type communication (MTC) coexistence within a broadband system, such as Long Term Evolution (LTE), in accordance with certain aspects of the present disclosure is illustrated.

[0037] Figure 6

[0013] Example operations for wireless communications by a UE are illustrated in accordance with certain aspects of the present disclosure.

[0038] Figure 7

[0013] Example operations for wireless communications by a BS are illustrated in accordance with certain aspects of the present disclosure.

[0039] Figure 8 An example of a call flow for a random access procedure in MTC and / or eMTC is illustrated.

[0040] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. DETAILED DESCRIPTION

[0041] Various aspects of the present disclosure provide random access procedures that can be used by devices operating in machine type communication (MTC) and / or eMTC. As will be described in more detail below, the techniques presented herein can allow devices in MTC and / or eMTC to determine (and / or adapt) the location, timing and / or size of one or more bundled messages (e.g., random access channel (RACH) preambles, random access response messages, connection request messages, and / or contention resolution messages) used in the random access procedures. As will be described in more detail below, the various aspects presented herein can also provide techniques for prioritizing broadcast transmissions in MTC and / or eMTC.

[0042] Various aspects of the present disclosure provide techniques for devices with limited communication resources, such as MTC devices (e.g., low-cost MTC devices, low-cost eMTC devices). Low-cost MTC devices can coexist with other traditional devices in a specific radio access technology (RAT) (e.g., long-term evolution (LTE), etc.) and can operate on one or more narrowband areas divided from the available system bandwidth supported by the specific RAT. Low-cost MTC devices can also support different operating modes, such as coverage enhancement mode (e.g., where repetitions of the same message can be bundled or transmitted across multiple subframes), normal coverage mode (e.g., where repetitions may not be transmitted), and the like.

[0043] The technology described in this article can be used for various wireless communication networks, such as code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) networks, single carrier FDMA (SC-FDMA) networks, etc. The terms "network" and "system" are often used interchangeably. A CDMA network can implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (W-CDMA), Time Division Synchronous CDMA (TD-SCDMA), and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. TDMA networks can implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Radio technologies such as LTE and GSM are used in the UMTS. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and Advanced LTE (LTE-A) in two forms of Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are new versions of UMTS using E-UTRA, which use OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). Cdma2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). The technology described herein can be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, certain aspects of these technologies are described below for LTE / LTE-A, and LTE / LTE-A terms are used in most of the following descriptions. LTE and LTE-A are generally referred to as LTE.

[0044] Figure 1 An example wireless communication network 100 with base stations (BSs) and user equipment (UEs) in which aspects of the present disclosure may be practiced is illustrated. For example, one or more UEs (e.g., low-cost MTC UEs, low-cost eMTC UEs, etc.) in the wireless communication network 100 may utilize a random access procedure described in more detail below to initiate communications with one or more BSs in the wireless communication network.

[0045] According to the techniques presented herein, the eNBs 110a, 110b, 110c, 110d (eNBs 110 for short) and the UEs 120a, 120b, 120c, 120d (UEs 120 for short) in the wireless communication network 100 may be able to determine (and / or adapt) the location (e.g., one or more narrowband regions within the available system bandwidth that may be used for the bundled message), timing (e.g., one or more subframes that may be used for the bundled message), and / or size (e.g., the number of the one or more subframes that may be used for the bundled message) of the bundled message for each bundled message used in the random access procedure. Furthermore, according to various aspects, one or more broadcast transmissions in MTC and / or eMTC that may be utilized in the wireless communication network 100 may be prioritized according to the techniques presented herein.

[0046] The wireless communication network 100 may be an LTE network or some other wireless network. The wireless communication network 100 may include several evolved Node Bs (eNBs) 110 and other network entities. An eNB is an entity that communicates with a user equipment (UE) and may also be referred to as a base station, a Node B, an access point (AP), etc. Each eNB may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" may refer to a coverage area of ​​an eNB and / or an eNB subsystem serving the coverage area, depending on the context in which the term is used.

[0047] An eNB may provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscriptions. A femto cell may cover a relatively small geographic area (e.g., a residence) and may allow restricted access by UEs associated with the femto cell (e.g., UEs in a closed subscriber group (CSG)). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a pico cell may be referred to as a pico eNB. An eNB for a femto cell may be referred to as a femto eNB or a home eNB (HeNB). In Figure 1 In the example shown in , eNB 110a may be a macro eNB for macro cell 102a, eNB 110b may be a pico eNB for pico cell 102b, and eNB 110c may be a femto eNB for femto cell 102c. An eNB may support one or more (e.g., three) cells. The terms "eNB," "base station," and "cell" may be used interchangeably herein.

[0048] The wireless communication network 100 may also include a relay station. A relay station is an entity that can receive transmissions of data from an upstream station (e.g., an eNB or UE) and send transmissions of the data to a downstream station (e.g., a UE or eNB). A relay station may also be a UE that can relay transmissions for other UEs. Figure 1 In the example shown in FIG. 1 , a relay (station) eNB 110 d may communicate with a macro eNB 110 a and a UE 120 d to facilitate communication between the eNB 110 a and the UE 120 d. A relay station may also be referred to as a relay eNB, a relay base station, a relay, etc.

[0049] The wireless communication network 100 may be a heterogeneous network including different types of eNBs, such as macro eNBs, pico eNBs, femto eNBs, relay eNBs, etc. These different types of eNBs may have different transmit power levels, different coverage areas, and different impacts on interference in the wireless communication network 100. For example, a macro eNB may have a high transmit power level (e.g., 5 to 40 Watts), while a pico eNB, a femto eNB, and a relay eNB may have a lower transmit power level (e.g., 0.1 to 2 Watts).

[0050] The network controller 130 may be coupled to a set of eNBs and may provide coordination and control for these eNBs. The network controller 130 may communicate with each eNB via a backhaul. The eNBs may also communicate with each other, for example, directly or indirectly via a wireless or wired backhaul.

[0051] UE 120 (e.g., 120a, 120b, 120c, etc.) may be dispersed throughout the wireless communication network 100, and each UE may be stationary or mobile. UE may also be referred to as an access terminal, terminal, mobile station (MS), subscriber unit, station (STA), etc. UE may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet device, a smart phone, a netbook, a smartbook, an ultrabook, an entertainment device (e.g., a music player, a gaming device, etc.), a camera, a vehicle-mounted device, a navigation device, a remote-controlled aircraft, a robot / robotic device, a wearable device (e.g., a smart watch, a smart garment, a smart wristband, a smart ring, a smart bracelet, smart glasses, virtual reality glasses), etc.

[0052] One or more UEs 120 in the wireless communication network 100 (e.g., an LTE network) may also be low-cost, low-data rate devices, such as, for example, low-cost MTC UEs, low-cost eMTC UEs, etc. Low-cost UEs may coexist with traditional and / or advanced UEs in the LTE network, and may have limited one or more capabilities when compared to other UEs (e.g., non-low-cost UEs) in the wireless network. For example, when compared to traditional and / or advanced UEs in the LTE network, the low-cost UE may operate according to one or more of the following: a reduction in maximum bandwidth (relative to traditional UEs), a single receive radio frequency (RF) chain, a reduction in peak rate, a reduction in transmit power, rank 1 transmission, half-duplex operation, etc. As used herein, devices with limited communication resources (such as MTC devices, eMTC devices, etc.) are generally referred to as low-cost UEs. Similarly, traditional devices (such as traditional and / or advanced UEs (e.g., in LTE)) are generally referred to as non-low-cost UEs.

[0053] As mentioned above, one or more UEs 120 in a wireless communication system may initiate communication with an eNB 110 using a random access procedure. The random access procedure may generally be used in various situations, such as initial access from a disconnected state or radio failure, a handover requiring a random access procedure, downlink or uplink data arrival during a connected state and thereafter the UE 120 has lost synchronization, uplink data arrival without a dedicated scheduling request channel available, and / or other various situations. Examples of random access procedures may include a contention-based random access procedure (which may be initiated on a random access channel (RACH)), and a contention-free (e.g., non-contention-based) random access procedure. The difference between the two procedures may be whether there is a possibility of failure using overlapping random access preambles.

[0054] As also mentioned above, according to certain aspects, the random access procedure may also be used in MTC and / or eMTC that may coexist with LTE in the wireless communication network 100. However, as will be described in more detail, due in part to support for narrowband operation and / or bundling in MTC and eMTC, the random access procedure used by one or more low-cost UEs 120 in MTC and / or eMTC may be different from the random access procedure used by non-low-cost UEs. Accordingly, various aspects presented herein provide techniques for random access procedures that may be utilized by low-cost UEs 120 in MTC and / or eMTC.

[0055] Figure 2 can be used as Figure 1 1. Block diagram of a design of a BS / eNB 110 and a UE 120 for one of the BS / eNBs 110 and one of the UEs 120 in FIG. BS 110 may be equipped with T antennas 234a through 234t, and UE 120 may be equipped with R antennas 252a through 252r, where in general, T≥1 and R≥1.

[0056] At BS 110, transmit processor 220 may receive data for one or more UEs from data source 212, select one or more modulation and coding schemes (MCS) for each UE based on a channel quality indicator (CQI) received from the UE, process (e.g., encode and modulate) the data for each UE based on the MCS selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI), etc.) and control information (e.g., CQI requests, grants, upper layer signaling, etc.), and provide overhead symbols and control symbols. Processor 220 may also generate reference symbols for reference signals (e.g., common reference signals (CRS)) and synchronization signals (e.g., primary synchronization signals (PSS) and secondary synchronization information (SSS)). A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on ​​data symbols, control symbols, overhead symbols, and / or reference symbols, where applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each MOD 232 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each MOD 232 may further process (e.g., convert to analog, amplify, filter, and up-convert) the output sample stream to obtain a downlink signal. The T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively.

[0057] At UE 120, antennas 252a to 252r may receive downlink signals from BS 110 and / or other BSs and may provide received signals to demodulators (DEMODs) 254a to 254r, respectively. Each DEMOD 254 may condition (e.g., filter, amplify, downconvert, and digitize) its received signals to obtain input samples. Each DEMOD 254 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all R demodulators 254a to 254r, perform MIMO detection on these received symbols where applicable, and provide detected symbols. A receive (RX) processor 258 may process (e.g., demodulate and decode) these detected symbols, provide decoded data for UE 120 to a data sink 260, and provide decoded control information and system information to a controller / processor 280. The channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), CQI, and the like.

[0058] On the uplink, at the UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information from a controller / processor 280 (e.g., for reports including RSRP, RSSI, RSRQ, CQI, etc.). The processor 264 may also generate reference symbols for one or more reference signals. The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266, where applicable, further processed by MODs 254a through 254r (e.g., for SC-FDM, OFDM, etc.), and transmitted to the BS 110. At the BS 110, uplink signals from the UE 120 and other UEs may be received by antennas 234, processed by DEMOD 232, detected by MIMO detector 236, where applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120. The processor 238 may provide the decoded data to a data sink 239 and the decoded control information to the controller / processor 240. BS 110 may include a communication unit 244 and communicate with network controller 130 via communication unit 244. Network controller 130 may include a communication unit 294, a controller / processor 290, and a memory 292.

[0059] Controllers / processors 240 and 280 may direct the operation at BS 110 and UE 120, respectively. For example, controller / processor 240 and / or other processors and modules at BS 110 may perform or direct the operation of Figure 7The operations 700 illustrated in FIG. 1 and / or other processes for the techniques described herein. Similarly, the controller / processor 280 and / or other processors and modules at the UE 120 may perform or direct the operation 700 illustrated in FIG. Figure 6 1. Operation 600 illustrated in FIG. 1, and / or processes for the techniques described herein. Memories 242 and 282 may store data and program codes for BS 110 and UE 120, respectively. Scheduler 246 may schedule UEs for data transmission on the downlink and / or uplink.

[0060] Figure 3 An exemplary frame structure 300 for FDD in LTE is shown. The transmission timeline for each of the downlink and uplink may be divided into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be divided into 10 subframes with indices 0 to 9. Each subframe may include two time slots. Each radio frame may thus include 20 time slots with indices 0 to 19. Each time slot may include L symbol periods, e.g., for a normal cyclic prefix (e.g., Figure 3 ) is 7 symbol periods, or 6 symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices 0 to 2L-1.

[0061] In LTE, an eNB may transmit a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) on the downlink in the center 1.08 MHz of the system bandwidth for each cell supported by the eNB. The PSS and SSS may be transmitted in symbol periods 6 and 5, respectively, in subframes 0 and 5 of each radio frame with a normal cyclic prefix, as shown in FIG. Figure 3 As shown in . The PSS and SSS can be used by the UE for cell search and acquisition. The eNB can transmit a cell-specific reference signal (CRS) across the system bandwidth for each cell supported by the eNB. The CRS can be transmitted in certain symbol periods of each subframe and can be used by the UE to perform channel estimation, channel quality measurement, and / or other functions. The eNB can also transmit a physical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 of certain radio frames. The PBCH can carry some system information. The eNB can transmit other system information in certain subframes, such as a system information block (SIB) on a physical downlink shared channel (PDSCH). The eNB can transmit control information / data on a physical downlink control channel (PDCCH) in the first B symbol periods of a subframe, where B can be configurable for each subframe. The eNB can transmit traffic data and / or other data on the PDSCH in the remaining symbol periods of each subframe.

[0062] The PSS, SSS, CRS and PBCH in LTE are described in the publicly available 3GPP TS 36.211 entitled "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation."

[0063] Figure 4 Two example subframe formats 410 and 420 for the downlink are shown with a normal cyclic prefix. The available time-frequency resources for the downlink may be divided into resource blocks. Each resource block may cover 12 subcarriers in a time slot and may include several resource elements. Each resource element may cover one subcarrier in a symbol period and may be used to send one modulation symbol, which may be a real value or a complex value.

[0064] Subframe format 410 may be used by an eNB equipped with two antennas. CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7, and 11. A reference signal is a signal known a priori to the transmitter and receiver and may also be referred to as a pilot. CRS is a cell-specific reference signal, for example, generated based on a cell identity (ID). Figure 4 , for a given resource element with label Ra, a modulation symbol may be transmitted from antenna a on the resource element, and no modulation symbol may be transmitted from other antennas on the resource element. Subframe format 420 may be used by eNBs equipped with four antennas. CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7, and 11 and from antennas 2 and 3 in symbol periods 1 and 8. For both subframe formats 410 and 420, CRS may be transmitted on uniformly spaced subcarriers, which may be determined based on a cell ID. Depending on the cell IDs of different eNBs, these eNBs may transmit their CRS on the same or different subcarriers. For both subframe formats 410 and 420, resource elements not used for CRS may be used to transmit data (e.g., traffic data, control data, and / or other data).

[0065] To implement FDD in LTE, an interleaving structure may be used for each of the downlink and uplink. For example, Q interleavings with indices 0 to Q-1 may be defined, where Q may be equal to 4, 6, 8, 10, or some other value. Each interleaving may include subframes spaced apart by Q frames. Specifically, interleaving q may include subframes q, q+Q, q+2Q, etc., where q∈{0,...,Q-1}.

[0066] The wireless network may support hybrid automatic repeat request (HARQ) for data transmission on the downlink and uplink. For HARQ, a transmitter (e.g., eNB 110) may send one or more transmissions of a packet until the packet is correctly decoded by a receiver (e.g., UE 120) or some other termination condition is encountered. For synchronous HARQ, all transmissions of the packet may be sent in each subframe of a single interlace. For asynchronous HARQ, each transmission of the packet may be sent in any subframe.

[0067] A UE may be located within the coverage of multiple eNBs. One of these eNBs may be selected to serve the UE. The serving eNB may be selected based on various criteria such as received signal strength, received signal quality, path loss, etc. Received signal quality may be quantified by signal-to-noise-and-interference ratio (SINR), or reference signal received quality (RSRQ), or some other metric. A UE may operate in a strong interference scenario, where the UE may observe severe interference from one or more interfering eNBs.

[0068] As mentioned above, one or more UEs in a wireless communication network (eg, wireless communication network 100) may be devices (such as low-cost UEs) with limited communication resources compared to other (non-low-cost) devices in the wireless communication network.

[0069] In some systems, for example, in LTE Rel-13, low-cost UEs may be limited to specific narrowband assignments within the available system bandwidth (e.g., no more than 6 resource blocks (RBs)). However, low-cost UEs may be able to re-tune to (e.g., operate and / or camp on) different narrowband regions within the available system bandwidth of an LTE system, for example, to coexist with an LTE system.

[0070] As another example of coexistence within an LTE system, a low-cost UE can (repeatedly) receive a legacy physical broadcast channel (PBCH) (e.g., an LTE physical channel that generally carries parameters that can be used for initial access to a cell) and support one or more legacy physical random access channel (PRACH) formats. For example, a low-cost UE can receive a legacy PBCH along with one or more additional repetitions of the PBCH across multiple subframes. As another example, a low-cost UE can transmit one or more repetitions of the PRACH (e.g., with one or more supported PRACH formats) to an eNB (e.g., eNB 110) in an LTE system. The PRACH can be used to identify the low-cost UE. In addition, the number of repeated PRACH attempts can be configured by the eNB.

[0071] The low-cost UE may also be a link-budget limited device and may operate in different operating modes based on its link budget limitations (e.g., using different numbers of repetitions for messages transmitted to or from the low-cost UE). For example, in some cases, the low-cost UE may operate in a normal coverage mode where there are few or no repetitions (e.g., the amount of repetitions required for the UE to successfully receive and / or transmit a message may be low or even no repetitions may be required). Alternatively, in some cases, the low-cost UE may operate in a coverage enhancement (CE) mode where there may be a large amount of repetitions. For example, for a 328-bit payload, a low-cost UE in CE mode may require 150 or more repetitions of the payload in order to successfully transmit and / or receive the payload.

[0072] In some cases (e.g., for LTE Rel-13), a low-cost UE may have limited capabilities with respect to its reception of broadcast transmissions (e.g., such as broadcast transmissions for system information blocks (SIBs), paging messages, random access response (RAR) messages, etc.) and unicast transmissions. For example, the maximum transport block (TB) size of a broadcast transmission received by a low-cost UE may be limited to 1000 bits. In addition, in some cases, a low-cost UE may not be able to receive more than one unicast TB in a subframe. In some cases (e.g., for both the CE mode and the normal mode described above), a low-cost UE may not be able to receive more than one broadcast TB in a subframe. In addition, in some cases, a low-cost UE may not be able to receive both unicast TBs and broadcast TBs in a subframe.

[0073] For MTC, low-cost UEs coexisting in the LTE system may also support new messages for certain procedures (such as paging, random access procedures, receiving broadcast system information, etc.) (e.g., different from the conventional messages used for these procedures in LTE). In other words, these new messages for paging, random access procedures, etc. may be separated from messages for similar procedures associated with non-low-cost UEs. For example, compared to conventional paging messages used in LTE, low-cost UEs may be able to monitor and / or receive paging messages that non-low-cost UEs may not be able to monitor and / or receive. Similarly, compared to conventional RAR messages used in conventional random access procedures, low-cost UEs may be able to receive RAR messages that non-low-cost UEs may not be able to receive. New paging and RAR messages associated with low-cost UEs may also be repeated one or more times (e.g., bundled). In addition, different numbers of repetitions (e.g., different bundle sizes) for these new messages may be supported.

[0074] Example MTC Coexistence in Broadband Systems

[0075] As mentioned above, MTC and / or eMTC operations may be supported in a wireless communication network (eg, the wireless communication network 100 ) (eg, co-existing with LTE or some other RAT). Figure 5A and 5B For example, an example is illustrated of how low-cost UEs in MTC operation can coexist with broadband systems (such as LTE).

[0076] like Figure 5A As illustrated in the example frame structure 500A of , subframes 502 associated with MTC and / or eMTC operations may be time division multiplexed (TDM) with regular subframes 504 associated with LTE (or some other RAT). As shown, in one example implementation, the number of subframes 502 associated with (e)MTC operations may be relatively small compared to the number of regular subframes 504.

[0077] Additionally or alternatively, such as Figure 5B As explained in the example frame structure of the subframe 500B of , one or more narrowbands used by low-cost UEs in MTC can be frequency-division multiplexed (FDM) in a wider bandwidth supported by LTE. Multiple narrowband areas can be supported for MTC and / or eMTC operations, wherein each narrowband area spans a bandwidth of no more than 6 RBs in total. In some cases, each low-cost UE in MTC operation can operate in one narrowband area (e.g., with 1.4MHz or 6 RBs) at a time. However, at any given time, the low-cost UE in MTC operation can be retuned to other narrowband areas in the wider system bandwidth. In some examples, multiple low-cost UEs can be served by the same narrowband area. In other examples, multiple low-cost UEs can be served by different narrowband areas (e.g., each narrowband area spans 6 RBs). In yet other examples, different combinations of low-cost UEs can be served by one or more identical narrowband areas and / or one or more different narrowband areas.

[0078] like Figure 5B As shown in FIG. 5 , in subframe 500B, the low-cost UE may monitor the wideband region 506 for legacy control information and monitor the wideband regions 508A and 508B for data. The low-cost UE may operate (e.g., monitor / receive / transmit) in the narrowband region for various operations. For example, Figure 5B As shown in , a first narrowband region 510 (e.g., spanning no more than 6 RBs) of a subframe may be monitored by one or more low-cost UEs to detect a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), MTC signaling, or a paging transmission from a BS in a wireless communication network. Figure 5BAs also shown in the figure, the low-cost UE can re-tune to the second narrowband region 512 of the subframe (e.g., also spanning no more than 6 RBs) to transmit the RACH or data previously configured in the signaling received from the BS. In some cases, the second narrowband region 512 can be utilized by the same low-cost UE that utilizes the first narrowband region 510 (e.g., the low-cost UE may have re-tuned to the second narrowband region for transmission after monitoring in the first narrowband region). In some cases (although not shown), the second narrowband region 512 can be utilized by a different low-cost UE than the low-cost UE that utilizes the first narrowband region 510.

[0079] Although the examples described herein assume a narrowband of 6 RBs, those skilled in the art will recognize that the techniques presented herein may also be applied to narrowband regions of different sizes.

[0080] Example Random Access Procedure for eMTC

[0081] As mentioned above, in some systems (e.g., LTE Rel-13 systems), narrowband operation for eMTC may be supported. In addition, as also mentioned above, different operation modes for low-cost devices (such as low-cost UEs in eMTC) may also be supported, which may use different amounts of repetition before a message is successfully received and / or transmitted by a low-cost UE.

[0082] According to certain aspects, the random access procedure in MTC and / or eMTC may also use narrowband operation and different amounts of bundling for different messages used in the random access procedure. Figure 8 As shown in, a low-cost UE and / or an eNB in ​​an eMTC may use (e.g., monitor / transmit / receive) a bundled (e.g., one or more repetitions) random access channel (RACH) preamble (MTC_MSG 1), a bundled random access response (RAR) message (MTC_MSG 2), a bundled connection request message (MTC_MSG 3), and / or a bundled contention resolution message (MTC_MSG 4) in a random access procedure. In addition, each bundled message used in the random access procedure may be transmitted / received in multiple subframes and in one or more narrowbands carved out in the available system bandwidth. In addition, the bundle size of each bundled message (e.g., the number of multiple subframes in which each bundled message is transmitted) may vary.

[0083] Therefore, in some cases, due to support for these features, it may be helpful to let the BS and / or low-cost UE know the specific manner (e.g., location, timing, and amount) in which each bundled message used in the random access procedure is transmitted / received.

[0084] Accordingly, as mentioned above, the various aspects presented herein provide techniques that allow low-cost UEs and BSs to determine (and / or adapt) the location (e.g., one or more narrowband areas within the available system bandwidth that can be used for the bundled message), timing (e.g., one or more subframes that can be used for the bundled message), and / or size (e.g., the number of the one or more subframes that can be used for the bundled message) of each bundled message used in a random access procedure.

[0085] Figure 6 600 for wireless communications in accordance with certain aspects of the present disclosure. Operations 600 may be performed by a UE, such as a low-cost UE, which may be Figure 1 and 2 One of the UE 120 illustrated in FIG.

[0086] Operations 600 may begin at 602, where the UE determines a plurality of subframes in which the UE may transmit a bundled RACH message to a BS. At 604, the UE determines at least one narrowband region within the subframes for transmitting the RACH message. At 606, the UE determines a bundling size for the RACH message, the bundling size indicating the number of the plurality of subframes in which the RACH message is transmitted. At 608, the UE transmits the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundling size.

[0087] Figure 7 700 for wireless communications in accordance with certain aspects of the present disclosure. Operations 700 may be performed by a BS such as Figure 1 and 2 Executed by one of the BS / eNBs 110 illustrated in FIG.

[0088] Operations 700 may begin at 702, where a BS determines a plurality of subframes in which a UE (e.g., a low-cost UE) may transmit a bundled RACH message to the BS. At 704, the BS determines at least one narrowband region within the subframes for receiving a RACH message. At 706, the BS determines a bundling size for the RACH message, the bundling size indicating the number of the plurality of subframes in which the RACH message is transmitted by the UE. At 708, the BS receives the RACH message in the narrowband region of the plurality of subframes based at least in part on the determined bundling size.

[0089] Figure 8 An example of a call flow 800 for a random access procedure in MTC and / or eMTC is illustrated. Figure 8 The eNB and MTC device (eg, low-cost UE) illustrated in the figure may be, for example, Figure 1-2 Any BS / eNB 110 and UE 120 illustrated in FIG.

[0090] In one reference example of a random access procedure (in MTC, eMTC, etc.), at 802, the UE 120 transmits a bundled RACH preamble (e.g., MTC_MSG 1) to the eNB 110 (e.g., to initiate communication with the eNB, etc.). The UE may select a RACH preamble for the RACH message from a set of RACH preambles. The UE may transmit the bundled RACH message (including the selected RACH preamble) to the eNB. According to certain aspects, the UE 120 transmits the bundled RACH message to the eNB 110 with one or more different bundle sizes (e.g., bundle sizes 1, 2, 3, etc.). For example, in some cases, the amount of bundling used to bundle the RACH message may be based in part on a particular coverage mode in which the UE 120 is operating (e.g., CE mode, normal mode, etc.). As mentioned above, when the UE 120 is operating in the normal mode, the UE 120 may use a lower amount of bundling than the amount of bundling used when the UE 120 is operating in the CE mode. However, in general, UE 120 and / or eNB 110 may support multiple bundling sizes for different coverage enhancements.

[0091] Accordingly, various aspects presented herein provide techniques that allow a UE 120 and / or an eNB 110 to determine a bundling size for a bundled RACH message transmitted to the eNB 110 in a random access procedure. In one aspect, the UE 120 and / or the eNB 110 may determine the bundling size for the bundled RACH message based at least in part on broadcast signaling from the eNB 110. As mentioned above, the broadcast signaling for indicating the bundling size may be separate broadcast signaling from the broadcast signaling for indicating system information to non-low-cost UEs.

[0092] According to certain aspects, UE 120 and / or eNB 110 may determine a bundling size for bundling RACH messages based at least in part on the location of one or more narrowband regions carved out in the available system bandwidth. For example, in some cases, each of the one or more narrowband regions may have a fixed bundling size that may be used for RACH transmissions. In some cases, each narrowband region may have a different fixed bundling size for RACH transmissions. In some cases, one or more narrowband regions may have the same fixed bundling size as one or more other narrowband regions.

[0093] In certain aspects, the one or more narrowband regions may support different coverage modes for UE 120, and the bundle size for RACH transmission may be determined at least in part based on the one or more narrowband regions supporting the particular coverage mode of UE 120. For example, in some cases, if UE 120 is operating in normal coverage mode, UE 120 may identify one or more narrowband regions that support its normal coverage mode. UE 120 may then determine the bundle size for RACH transmission, for example, based at least in part on the fixed bundle size used by the one or more narrowband regions supporting the normal coverage mode. Similar examples may apply to CE mode and / or other modes of UE 120.

[0094] According to certain aspects, UE 120 and / or eNB 110 may determine a bundle size for a bundled RACH message based at least in part on a starting subframe of the bundled RACH message. For example, within each of the one or more narrowband regions, multiple bundle sizes may be supported. In one scenario, within a particular narrowband region, a first set of subframes may have a particular bundle size for RACH transmissions, while a second set of subframes may have another bundle size for other transmissions. In these scenarios, within each of the one or more narrowband regions, the bundle size for bundled RACH transmissions may vary depending on the subframe in which the bundled RACH transmission may start (e.g., in the first set of subframes).

[0095] According to certain aspects, UE 120 and / or eNB 110 may determine a bundling size for bundling RACH messages based at least in part on an estimated CE target for a low-cost UE (e.g., for CE mode). For example, UE 120 (and / or eNB 110) may identify an estimated CE target that may be used for RACH transmissions based at least in part on a radio quality condition between UE 120 and eNB 110. In one scenario, UE 120 may determine the estimated CE target using a downlink (DL) path loss. For example, based on the DL path loss, UE 120 may determine that UE 120 should operate in CE mode and use a relatively larger bundling size for bundling RACH (e.g., compared to a bundling size for normal mode). In other examples, UE 120 may determine one or more other bundling sizes for bundling RACH (e.g., based on other quality measurements).

[0096] According to certain aspects, UE 120 and / or eNB 110 may determine a bundle size for a bundled RACH message based on a success or failure of eNB 110 to successfully decode a previously transmitted bundled RACH message. For example, in some cases, if UE 120 successfully decodes a random access response (RAR) message from eNB 110 for a previously transmitted bundled RACH (e.g., MTC_MSG 1), UE 120 may determine that (eNB 110 decoded a previously transmitted bundled RACH message, such as MTC_MSG 1) was successful. Similarly, in some cases, if UE 120 cannot successfully decode a RAR message from eNB 110 for a previously transmitted bundled RACH, UE 120 may determine that (eNB 110 decoded a previously transmitted bundled RACH message) was unsuccessful. In some cases (eg, if UE 120 determines failure), UE 120 may increase the bundle size relative to the bundle size used for the previous bundled RACH message in response to eNB 110 failing to successfully decode the previous bundled RACH message.

[0097] Additionally or alternatively, in some cases, in response to the eNB 110 failing to successfully decode a previous bundled RACH message, the UE 120 may increase the transmit power relative to the transmit power used to transmit the previous bundled RACH message. In certain aspects, the transmit power may be increased for the bundle size used for the previous bundled RACH message and / or for the bundle size of the subsequently transmitted bundled RACH message. Furthermore, when transmitting a bundled RACH message, a RACH counter at the UE 120 may be increased only once per bundled RACH message (e.g., as opposed to increasing the RACH counter for each RACH message transmitted within a single bundled RACH).

[0098] As mentioned above, various aspects presented herein also provide techniques that allow UE 120 and / or eNB 110 to determine a plurality of subframes in which UE 120 may transmit a bundled RACH to eNB 110. In one aspect, the plurality of subframes may be determined based at least in part on a particular subframe that may serve as a starting subframe for a bundled RACH message.

[0099] For example, if the UE 120 and / or the eNB 110 determines that the bundle size for the bundled RACH is 4, then in one case, each bundled RACH transmission may start at subframes 0, 4, 8, etc. (e.g., where each RACH transmission of the bundled RACH may occur in consecutive subframes). In another case, for example, with the same bundle size of 4 for the bundled RACH, each RACH transmission of the bundled RACH transmission may start at subframes 0, 2, 4, 6, etc. (e.g., where each RACH transmission of the bundled RACH occurs in non-consecutive subframes). However, in general, determining the starting subframe for each bundled RACH transmission may be based at least in part on the particular subframe uplink / downlink configuration used in that frame.

[0100] like Figure 8 As shown in , as part of the random access procedure, at 804, in response to receiving a bundled RACH message from UE 120, eNB 110 transmits a bundled RAR message (e.g., MTC_MSG 2) to UE 120. The UE may determine RAR resources on which to receive the RAR message based at least in part on the RACH preamble, and receive the RAR message on these RAR resources. The RAR resources may include at least one of a narrowband frequency region of a carrier bandwidth, a starting transmission time, a starting subframe, or a bundle size. In some cases, the bundled RAR message may not support HARQ. As shown in FIG. Figure 8 As shown in , the bundle size of the bundled RAR message may be based at least in part on the bundled RACH message.

[0101] In some aspects, the UE may also identify one or more control channel decoding candidates based at least in part on the RACH preamble, and blindly decode the one or more control channel candidates. In some cases, identifying one or more control channel decoding candidates may include determining at least one of a degree of aggregation (e.g., a number of control channel elements (CCEs) and / or enhanced control channel elements (eCCEs)), a RAR message bundle size, or a RAR message packet size. The UE may determine the RAR message packet size based at least in part on the RACH preamble. In some cases, the UE may select the RACH preamble based at least in part on the bundle size of the RAR message.

[0102] In certain aspects, the UE 120 and / or the eNB 110 may determine a bundle size and / or narrowband region for bundling the RAR messages based at least in part on the RACH message selected by the UE. The RAR message bundle size and / or narrowband region may further depend on at least one of the narrowband region or the bundle size of the bundled RACH message. For example, in some cases, the bundle size of the bundled RAR message may be the same as the bundle size of the bundled RACH message received from the low-cost UE (e.g., in Figure 8 In one implementation shown in , the bundle size is 4). In some cases, the bundle size of the bundled RAR message can be determined from the bundle size used in one or more narrowband regions for transmitting the bundled RACH message. In some cases, the bundle size of the RAR message can be independent of the bundle size of the PRACH message.

[0103] In certain aspects, the control and / or data portions of a RAR message may be bundled. For example, the control portion of a RAR message may have a bundle size that is the same as or different from the bundle size used for the data portion of the RAR message. In some aspects, the bundle size and / or narrowband region used for the control portion of a RAR message (e.g., on an ePDCCH) may be implicitly determined based at least in part on at least one property of a corresponding RACH message selected by a UE. For example, determining the narrowband region for the control portion of a RAR message and / or the bundle size for transmitting the control portion of a RAR message may be based at least in part on the bundle size and / or narrowband region used to transmit a RACH message. In some cases, there may be a one-to-one mapping from the bundle size and / or narrowband region used for a RACH message to the bundle size and / or narrowband region used for the control portion of a RAR message.

[0104] According to certain aspects, the timing of the bundled RAR message may be based at least in part on the bundle size of the RACH message.For example, after transmitting a bundled RACH message, UE 120 may expect a bundled RAR message within a certain time period following the transmission of the bundled RACH.

[0105] In a conventional random access procedure (e.g., used by non-low-cost UEs), this time period may only last for a certain time period (e.g., about 10 ms). However, in eMTC, due to bundling, subframe configuration, etc., this time period may not be a sufficient time period for a low-cost UE to detect whether a bundled RAR is successfully received. For example, as mentioned above, in part due to bundling, the first subframe of the RAR (including the control part) may have to start at a specific subframe.

[0106] Accordingly, the techniques presented herein may allow this period to be extended (e.g., in eMTC) to allow low-cost UEs more time to detect bundled RAR transmissions rather than declaring RACH failure. In some cases, the calculation of the random access radio network temporary identifier (RA-RNTI) used to address the bundled RAR message may be different from the calculation used in the traditional random access procedure. For example, in eMTC, the RA-RNTI calculation may use the subframe in which the bundled RACH starts or ends.

[0107] In certain aspects, the bundled RAR provides a grant for transmitting a connection request message. For example, the bundled RAR message may contain various amounts of information that may be used by the low-cost UE to transmit / receive one or more subsequent bundled messages in a random access procedure (e.g., in an UL grant). Figure 8 As shown in , for example, both the bundled connection request message (eg, MTC_MSG3 at 806) and / or the bundled contention resolution message (eg, MTC_MSG4 at 808) may be based at least in part on the bundled RAR message.

[0108] In some cases, the bundled RAR message may indicate (via UL grant) at least one of a narrowband area or a bundle size for UE 120 to transmit a bundled connection request message (e.g., MTC_MSG 3) to eNB 110. Alternatively or additionally, in some cases, the bundled RAR message may also indicate (via UL grant) a narrowband area or a bundle size for UE 120 to receive a bundled contention resolution message (e.g., MTC_MSG 4) from eNB 110.

[0109] In certain aspects, the RAR grant within the bundled RAR message may be defined differently from the RAR grant used in the traditional random access procedure. For example, for non-low-cost UEs, the RAR grant may be 20 bits and may include 1 bit for a hopping flag, 10 bits for a fixed-size resource block assignment, 4 bits for a truncated modulation and coding scheme, 3 bits for a transmit / transmit power control (TPC) command for a scheduled physical uplink shared channel (PUSCH), 1 bit for UL delay, and 1 bit for a channel state information request.

[0110] According to certain aspects, for low-cost UEs in eMTC (e.g., under TTI bundling), the RAR grant within the bundled RAR message may be 12 bits and may include 2 bits for a transport block size (TBS) indicator, 4 bits for an UL resource block assignment indicator, 3 bits for a bundle length and a subband hopping indicator, and 3 bits for a TPC mode indicator and a TPC command. In some cases, the TBS indicator may indicate a quadrature phase shift keying (QPSK) modulation and coding scheme (MCS). In some cases, the UL resource block assignment indicator may be used to indicate a specific resource allocation within a subband (e.g., a narrowband region) of 6 resource blocks. In some cases, the bundle length and subband hopping indicator may indicate a specific bundle length and a subband hopping sequence for a given bundle length. For example, for a given bundle length of 32, the bundle length and subband hopping indicator may indicate that there should be 8 message blocks, each of which hops in 4 different subbands. In some cases, the TPC mode indicator may indicate whether the low-cost UE should operate in one or more transmit power modes. For example, the TPC mode indicator may indicate that the low-cost UE should operate in a maximum power mode or some other power mode. Alternatively, one or more TPC commands may be used within the RAR grant to indicate which power the low-cost UE should transmit at.

[0111] As mentioned above, after the eNB 110 transmits the bundled RAR message to the UE 120 at 804, the UE 120 may use various information in the bundled RAR message (e.g., information provided in the RAR grant defined above) to transmit a bundled radio resource control (RRC) connection request message (e.g., MTC_MSG 3) to the eNB 110 at 806. In other words, the RAR message may provide a grant for transmitting the connection request message, and the grant may indicate information such as TBS, bundle length, subband hopping indicator, TPC, etc. for the connection request message. In some cases, as described above, the specific narrowband region and / or bundle size of the bundled RRC connection request message may be indicated by the received bundled RAR message.

[0112] Additionally, certain aspects presented herein may allow for the transmission timing of the bundled RRC connection request message to vary (e.g., from a legacy random access procedure). For example, in general, for legacy random access procedures, the transmission timing of the transmission of the connection request message is controlled by the reception timing of the grant in the RAR message. However, in eMTC, due to bundling and / or narrowband operation, the transmission timing of the bundled RRC connection request message may have to be adapted depending on the amount of bundling used to bundle the RAR and the bundled connection request message.

[0113] Accordingly, the techniques presented herein may allow the timing of transmitting a connection request message to be based at least in part on the bundle size of the bundled RAR message and / or the bundle size of the connection request message. For example, the UE 120 may start transmission of the bundled connection request message on the first uplink subframe k+n (n>n1) upon decoding the RAR grant in the bundled RAR message in a particular subframe k, where n1 includes time for the UE 120 to prepare a new UL packet and / or perform a possible narrowband retuning.

[0114] Additionally, in some cases, the amount of bundling used for the bundled connection request message may depend on the narrowband region in which UE 120 is operating and / or the time required to re-tune to another narrowband region. For example, as mentioned above, in some cases, the bundled connection request transmission may start in a specific subframe and the amount of bundling may depend on the number of available subframes remaining in the narrowband region that can be used for uplink transmission.

[0115] After UE 120 transmits the bundled connection request message to eNB 110 at 806, UE 120 may expect to receive a bundled contention resolution message (e.g., MTC_MSG 4) from eNB 110. As mentioned above, in some cases, the narrowband region and / or the bundle size used for the bundled contention resolution message may be determined based at least in part on an indication in the bundled RAR message received from eNB 110. However, in some cases, if the narrowband region and / or the bundle size used for the bundled contention resolution message is not indicated in the bundled RAR message, the bundled contention resolution message may be transmitted in the same narrowband region in which the bundled RAR message was transmitted and / or use the same bundle size used by the bundled RAR message.

[0116] Although the techniques described herein may be used for random access procedures in MTC and eMTC, one of ordinary skill in the art will appreciate that the techniques presented herein may also be applied to other procedures in MTC and / or eMTC, such as paging, transmitting / receiving system information, etc.

[0117] Example broadcast transmission prioritization for eMTC

[0118]

[0013] Various aspects presented herein also provide techniques for prioritizing broadcast transmissions in MTC and / or eMTC.

[0119] As mentioned above, in some cases, a low-cost UE may not be able to receive more than a single broadcast TB at any given time. For example, for each subframe, a low-cost UE may only be able to receive any one of a RAR message, a paging message, or broadcast signaling, etc. at a time. In addition, although different broadcast transmissions may occur in different narrowband regions, the BS may be able to broadcast transmissions for each narrowband region at the same time. Therefore, in some cases, there may be times when a low-cost UE is expecting a specific broadcast transmission from a BS but the BS may not be transmitting the specific broadcast transmission.

[0120] Accordingly, the techniques herein provide priority rules for devices in eMTC to follow when transmitting / receiving broadcast transmissions.

[0121] In certain aspects, the low-cost UE may apply one or more priority rules when determining the type of message (e.g., broadcast transmission) to obtain from the BS. For example, the broadcast transmission (from the BS) may be a (bundled) random access response, a (bundled) paging message, a broadcast message carrying system information from the BS, etc. In some cases, the low-cost UE may apply the priority rules after transmitting a RACH message to the BS.

[0122] In one specific implementation, the low-cost UE may define receiving bundled RAR messages (e.g., because the RAR message may be triggered by the transmitted RACH) as a first priority, receiving paging messages (e.g., which may be used for incoming data notifications and system information updates) as a second priority, and receiving system information (e.g., which generally may not need to be received frequently and may also be indicated via paging) as a third priority.

[0123] Thus, in the above example, if the low-cost UE has transmitted a bundled RACH message and has not received a bundled RAR message from the BS, the low-cost UE may determine to monitor the broadcasted bundled RAR message before monitoring the paging message and the system information. However, if the low-cost UE has not transmitted a bundled RACH message or has received a RAR message, the low-cost UE may determine to monitor the broadcasted paging message before monitoring the broadcasted system information, etc.

[0124] However, in general, although the above examples describe a specific priority order for obtaining broadcast transmissions from a BS in eMTC, one of ordinary skill in the art will appreciate that other priorities may also be defined for broadcast transmissions in MTC and / or eMTC.

[0125] As used herein, a phrase referring to "at least one" of a list of items refers to any combination of those items, including single members. As an example, "at least one of a, b, or c" is intended to cover: a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c).

[0126] As used herein, the term "determining" encompasses a wide variety of actions. For example, "determining" may include calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, database, or other data structure), ascertaining, and the like. Also, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Also, "determining" may also include resolving, selecting, choosing, establishing, and the like.

[0127] In some cases, rather than actually communicating frames, a device may have an interface for communicating frames for transmission or reception. For example, for transmission, a processor may output a frame to an RF front end via a bus interface. Similarly, rather than actually receiving a frame, a device may have an interface for acquiring a frame received from another device. For example, for transmission, a processor may obtain (or receive) a frame from an RF front end via a bus interface.

[0128] The methods disclosed herein include one or more steps or actions for implementing the described methods. These method steps and / or actions may be interchangeable with each other without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be changed without departing from the scope of the claims.

[0129] The various operations of the methods described above may be performed by any suitable device capable of performing the corresponding functions. One or more processors, circuits, or other devices may execute software. Software should be broadly interpreted as meaning instructions, instruction sets, codes, code segments, program codes, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether they are described in software, firmware, middleware, microcode, hardware description language, or other terms. These devices may include various hardware and / or software components and / or modules, including but not limited to circuits, application specific integrated circuits (ASICs), or processors. In general, where operations are explained in the accompanying drawings, those operations may be performed by any suitable corresponding paired devices plus functional components.

[0130] For example, the means for receiving and / or the means for monitoring may include a receiver such as Figure 2 The receive processor 238, MIMO detector 236, demodulators 232a-232t, and / or antennas 234a-234t of the base station 110 illustrated in FIG. Figure 2 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, Figure 2 Controller / processor 240, scheduler 246, transmit processor 220, receive processor 238, MIMO detector 236, TX MIMO processor 230, and / or modulator / demodulators 232a-232t of base station 110 illustrated in FIG. Figure 2 1, a controller / processor 280, a receive processor 258, a transmit processor 264, a MIMO detector 256, a TX MIMO processor 266, and / or modulators / demodulators 254a-254r of the user equipment 120 illustrated in FIG. The means for signaling, the means for providing, the means for transmitting, the means for increasing, and / or the means for indicating may include a transmitter, such as Figure 2 The transmit processor 220, TX MIMO detector 230, modulators 232a-232t, and / or antennas 234a-234t of the base station 110 illustrated in FIG. Figure 2 1. The transmit processor 264, TX MIMO processor 266, modulators 254a-254r, and / or antennas 252a-252r of the user equipment 120 are illustrated in FIG.

[0131] Those skilled in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or a combination thereof.

[0132] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the disclosure herein may be implemented as hardware, software, or a combination thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. The technician may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0133] The various illustrative logical blocks, modules, and circuits described in conjunction with the disclosure herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0134] The steps of the method or algorithm described in conjunction with the disclosure herein can be implemented directly in hardware, in a software module executed by a processor, or in a combination thereof. The software module can reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a phase change memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read / write information from / to the storage medium. Alternatively, the storage medium can be integrated into the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In an alternative, the processor and the storage medium can reside in a user terminal as discrete components.

[0135] In one or more exemplary designs, the functions described can be implemented in hardware, software, or a combination thereof. If implemented in software, each function can be stored on or transmitted by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any media that facilitates the transfer of a computer program from one place to another. Storage media can be any available media that can be accessed by a general or special-purpose computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD / DVD or other optical disk storage, disk storage or other magnetic storage devices, or any other medium that can be used to carry or store the desired program code means in the form of instructions or data structures and can be accessed by a general or special-purpose computer, or a general or special-purpose processor. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of the medium. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wherein disk often reproduces data magnetically while disc reproduces data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0136] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the universal principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for wireless communication by a user equipment UE, comprising: determining a plurality of subframes in which the UE can transmit a bundled random access channel, RACH, preamble to a base station BS, wherein the plurality of subframes is determined at least in part based on a specific subframe that can be used as a starting subframe of the bundled RACH preamble; determining at least one narrowband region within the plurality of subframes for transmitting the clustered RACH preamble; for each of at least one narrowband region, determining a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted, wherein the bundle size varies depending on the starting subframe; transmitting the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as A bundled random access response message is received from the BS.

2. The method of claim 1, further comprising: determining a narrowband region of a contention resolution message from the BS based at least in part on a narrowband region of the bundled random access response message; as well as A contention resolution message is received from the BS over the determined narrowband area of ​​the contention resolution message.

3. The method of claim 1, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on broadcast signaling from the BS.

4. The method of claim 1, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on an estimated coverage enhancement target.

5. The method of claim 1, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on a success or failure of the BS to successfully decode a previous bundled RACH preamble.

6. The method of claim 5, wherein: The success or failure is determined based at least in part on successfully decoding a random access response message from the BS for a previously transmitted bundled RACH preamble.

7. The method of claim 5, further comprising, in response to the BS failing to successfully decode the previous bundled RACH preamble, performing at least one of the following: increasing the bundle size used for the bundled RACH preamble relative to the bundle size used for the previous bundled RACH preamble; or The transmit power for the bundled RACH preamble is increased relative to the transmit power for the previous bundled RACH preamble.

8. The method of claim 1, wherein: At least one of a narrowband region or a bundle size of the control portion of the bundled random access response message is based at least in part on determining at least one property from the selected bundled RACH preamble.

9. The method of claim 8, wherein: The at least one property includes at least one of the at least one narrowband region of the bundled RACH preamble or the bundle size.

10. The method of claim 1, wherein: The timing of the bundled random access response message is based at least in part on the bundle size of the bundled RACH preamble.

11. The method of claim 1, wherein: The bundled random access response message indicates at least one of a narrowband area or a bundle size for the UE to transmit a connection request message.

12. The method of claim 1, wherein: The bundled random access response message indicates at least one of a narrowband region of a contention resolution message or a bundle size of the contention resolution message.

13. The method of claim 1, wherein: The bundled random access response message provides a grant for transmitting a connection request message, the grant indicating information about at least one of: a transport block size TBS, a bundle length, a subband hopping indicator, or a transmit power control TPC.

14. The method of claim 1, wherein: The timing of transmitting the connection request message is based at least in part on a bundle size of at least one of the bundled random access response message or the connection request message.

15. The method of claim 1, further comprising: applying the priority of the UE to determine a message type to be obtained from the BS, wherein the message type comprises one of a random access response message, a paging message, or a broadcast message carrying system information; as well as Monitoring the type of messages from the BS is performed based at least in part on the priority of the UE.

16. An apparatus for wireless communication, comprising: means for determining a number of subframes in which the equipment can transmit a bundled random access channel, RACH, preamble to a base station BS, wherein the number of subframes is determined at least in part based on a specific subframe that can serve as a starting subframe for the bundled RACH preamble; means for determining at least one narrowband region within the plurality of subframes for transmitting the clustered RACH preamble; means for determining, for each of at least one narrowband region, a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted, wherein the bundle size varies depending on the starting subframe; means for transmitting the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as means for receiving a bundled random access response message from the BS.

17. The apparatus of claim 16, further comprising: means for determining a narrowband region of a contention resolution message from the BS based at least in part on a narrowband region of the bundled random access response message; as well as means for receiving a contention resolution message from the BS over the determined narrowband region of the contention resolution message.

18. The apparatus of claim 16, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on broadcast signaling from the BS.

19. The apparatus of claim 16, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on an estimated coverage enhancement target.

20. The apparatus of claim 16, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on a success or failure of the BS to successfully decode a previous bundled RACH preamble.

21. The apparatus of claim 20, further comprising means for decoding a random access response message, wherein the success or failure is determined based at least in part on successfully decoding the random access response message from the BS for a previously transmitted bundled RACH preamble.

22. The apparatus of claim 20, further comprising means for increasing at least one of: increasing the bundle size used for the bundled RACH preamble relative to the bundle size used for the previous bundled RACH preamble; or The transmit power for the bundled RACH preamble is increased relative to the transmit power for the previous bundled RACH preamble.

23. The apparatus of claim 16, wherein: At least one of a narrowband region or a bundle size of the control portion of the bundled random access response message is based at least in part on determining at least one property from the selected bundled RACH preamble.

24. The apparatus of claim 16, wherein: The at least one property includes at least one of the at least one narrowband region of the bundled RACH preamble or the bundle size.

25. The apparatus of claim 16, wherein: The timing of the bundled random access response message is based at least in part on the bundle size of the bundled RACH preamble.

26. The apparatus of claim 16, further comprising means for transmitting a connection request message, wherein the bundled random access response message indicates at least one of a narrowband region or a bundle size for the apparatus to transmit the connection request message.

27. The apparatus of claim 16, wherein: The bundled random access response message indicates at least one of a narrowband region of a contention resolution message or a bundle size of the contention resolution message.

28. The apparatus of claim 16, further comprising means for transmitting a connection request message, wherein the bundled random access response message provides a grant for transmitting the connection request message, the grant indicating information about at least one of: a transport block size TBS, a bundle length, a subband hopping indicator, or a transmit power control TPC.

29. The apparatus of claim 16, further comprising means for transmitting a connection request message, wherein a timing of transmitting the connection request message is based at least in part on a bundle size of at least one of the bundled random access response message or the connection request message.

30. The apparatus of claim 16, further comprising: means for applying the priority of the equipment for determining a message type to be obtained from the BS, wherein the message type comprises one of a random access response message, a paging message, or a broadcast message carrying system information; as well as Means for monitoring the type of messages from the BS based at least in part on the priority of the equipment.

31. An apparatus for wireless communication, comprising: at least one processor; as well as a memory coupled to the at least one processor, the memory storing instructions executable by the at least one processor to cause the apparatus to: determining a plurality of subframes in which the apparatus can transmit a bundled random access channel, RACH, preamble to a base station BS, wherein the plurality of subframes is determined at least in part based on a specific subframe that can serve as a starting subframe of the bundled RACH preamble; determining at least one narrowband region within the plurality of subframes for transmitting the clustered RACH preamble; for each of at least one narrowband region, determining a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted, wherein the bundle size varies depending on the starting subframe; transmitting the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as A bundled random access response message is received from the BS.

32. A computer-readable medium for wireless communication by a user equipment UE, wherein the computer-readable medium has computer executable code stored thereon, and when the code is executed by a processor, the following steps are implemented: determining a plurality of subframes in which the UE can transmit a bundled random access channel, RACH, preamble to a base station BS, wherein the plurality of subframes is determined at least in part based on a specific subframe that can be used as a starting subframe of the bundled RACH preamble; determining at least one narrowband region within the plurality of subframes for transmitting the clustered RACH preamble; for each of at least one narrowband region, determining a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted, wherein the bundle size varies depending on the starting subframe; transmitting the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as A bundled random access response message is received from the BS.

33. A method for wireless communication by a base station BS, comprising: determining a plurality of subframes in which a user equipment (UE) can transmit a bundled random access channel (RACH) preamble to the BS, wherein the plurality of subframes is determined at least in part based on a particular subframe that can serve as a starting subframe of the bundled RACH preamble; Determining at least one narrowband region within the plurality of subframes for receiving the clustered RACH preamble; for each of at least one narrowband region, determining a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted by the UE, wherein the bundle size varies depending on the starting subframe; receiving the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as Transmit a Bundled Random Access Response message.

34. The method of claim 33, further comprising: determining a narrowband region of a contention resolution message based at least in part on a narrowband region of the bundled random access response message; as well as The contention resolution message is transmitted over the determined narrowband area of ​​the contention resolution message.

35. The method of claim 33, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on broadcast signaling from the BS.

36. The method of claim 33, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on an estimated coverage enhancement target.

37. The method of claim 33, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on a success or failure of the BS to successfully decode a previous bundled RACH preamble.

38. The method of claim 37, wherein: The success or failure is determined based at least in part on the UE successfully decoding a random access response message from the BS for a previous bundled RACH preamble.

39. The method of claim 33, wherein: At least one of a narrowband region or a bundle size of a control portion of the bundled random access response message is determined based at least in part on determining at least one property from the bundled RACH preamble.

40. The method of claim 39, wherein: The at least one property from the bundled RACH preamble includes at least one of the at least one narrowband region of the bundled RACH preamble or the bundle size.

41. The method of claim 33, wherein: The timing of the random access response message is based at least in part on the bundle size of the bundled RACH preamble.

42. The method of claim 33, wherein: The bundled random access response message indicates at least one of a narrowband area or a bundle size for the UE to transmit a connection request message.

43. The method of claim 33, wherein: The bundled random access response message indicates at least one of a narrowband region of a contention resolution message or a bundle size of the contention resolution message.

44. The method of claim 33, wherein: The bundled random access response message provides a grant for transmitting a connection request message, the grant indicating information about at least one of: a transport block size TBS, a bundle length, a subband hopping indicator, or a transmit power control TPC.

45. The method of claim 33, wherein: The timing of receiving the connection request message is based at least in part on a bundle size of at least one of the bundled random access response message or the connection request message.

46. ​​An apparatus for wireless communication, comprising: means for determining a plurality of subframes in which a user equipment (UE) can transmit a bundled random access channel (RACH) preamble to the equipment, wherein the plurality of subframes is determined based at least in part on a particular subframe that can serve as a starting subframe for the bundled RACH preamble; means for determining at least one narrowband region within the plurality of subframes for receiving the bundled RACH preamble; means for determining, for each of at least one narrowband region, a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted by the UE, wherein the bundle size varies depending on the starting subframe; means for receiving the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as Means for transmitting a bundled random access response message.

47. The apparatus of claim 46, wherein the apparatus further comprises: means for determining a narrowband region of a contention resolution message based at least in part on the narrowband region of the bundled random access response message; as well as Means for transmitting the contention resolution message over the determined narrowband area of ​​the contention resolution message.

48. The apparatus of claim 46, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on broadcast signaling from the equipment.

49. The apparatus of claim 46, wherein: The bundling size for the bundled RACH preamble is further determined based at least in part on an estimated coverage enhancement target.

50. The apparatus of claim 46, wherein: The bundle size for the bundled RACH preamble is further determined based at least in part on a success or failure of the apparatus to successfully decode a previous bundled RACH preamble.

51. The apparatus of claim 50, wherein: The success or failure is determined based at least in part on the UE successfully decoding a random access response message from the equipment for a previous bundled RACH preamble.

52. The apparatus of claim 46, wherein: At least one of a narrowband region or a bundle size of a control portion of the bundled random access response message is based at least in part on determining at least one property from the bundled RACH preamble.

53. The apparatus of claim 52, wherein: The at least one property from the bundled RACH preamble includes at least one of the at least one narrowband region of the bundled RACH preamble or the bundle size.

54. The apparatus of claim 46, wherein: The timing of the bundled random access response message is based at least in part on the bundle size of the bundled RACH preamble.

55. The apparatus of claim 46, wherein: The bundled random access response message indicates at least one of a narrowband area or a bundle size for the UE to transmit a connection request message.

56. The apparatus of claim 46, wherein: The bundled random access response message indicates at least one of a narrowband region of a contention resolution message or a bundle size of the contention resolution message.

57. The apparatus of claim 46, wherein: The bundled random access response message provides a grant for transmitting a connection request message, the grant indicating information about at least one of: a transport block size TBS, a bundle length, a subband hopping indicator, or a transmit power control TPC.

58. The apparatus of claim 46, further comprising means for receiving a connection request message, wherein a timing of receiving the connection request message is based at least in part on a bundle size of at least one of the bundled random access response message or the connection request message.

59. An apparatus for wireless communication, comprising: at least one processor; as well as a memory coupled to the at least one processor, the memory storing instructions executable by the at least one processor to cause the apparatus to: determining a plurality of subframes in which a user equipment (UE) can transmit a bundled random access channel (RACH) preamble to the apparatus, wherein the plurality of subframes is determined at least in part based on a particular subframe that can serve as a starting subframe for the bundled RACH preamble; Determining at least one narrowband region within the plurality of subframes for receiving the clustered RACH preamble; for each of at least one narrowband region, determining a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted by the UE, wherein the bundle size varies depending on the starting subframe; receiving the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as Transmit a Bundled Random Access Response message.

60. A computer-readable medium for wireless communication by a base station BS, the computer-readable medium having computer executable code stored thereon, the code implementing the following steps when executed by a processor: determining a plurality of subframes in which a user equipment (UE) can transmit a bundled random access channel (RACH) preamble to the BS, wherein the plurality of subframes is determined at least in part based on a particular subframe that can serve as a starting subframe of the bundled RACH preamble; Determining at least one narrowband region within the plurality of subframes for receiving the clustered RACH preamble; for each of at least one narrowband region, determining a bundle size for the bundled RACH preamble based at least in part on a starting subframe of the bundled RACH preamble, the bundle size indicating a number of the plurality of subframes in which the bundled RACH preamble is transmitted by the UE, wherein the bundle size varies depending on the starting subframe; receiving the bundled RACH preamble in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundle size; as well as Transmit a Bundled Random Access Response message.

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