Random access procedure and broadcast prioritization for machine type communications (MTC)

Abstract

To provide random access procedures of broadcast transmissions in machine type communications (MTC) devices and enhanced MTC (eMTC).SOLUTION: A method generally includes: determining a plurality of subframes in which UE may transmit a bundled random access channel (RACH) message to a base station (BS); determining, within the subframes, at least one narrowband region for transmitting the bundled RACH message; determining a bundling size for the bundled RACH message, the bundling size indicating the number of the 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 bundling size.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0001] 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 three of these applications are assigned to the assignee of this application and are hereby expressly incorporated by reference herein.

[0002]

[0002] Some aspects of the present disclosure generally relate to wireless communication, and more particularly, to random access procedures and / or prioritization of broadcast transmissions in machine - type communication (MTC) devices and extended or evolved MTC (eMTC).

Background Art

[0003]

[0003] Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, etc. These systems can be multiple - access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth and transmission 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, the 3rd Generation Partnership Project (3GPP (registered trademark)) LTE, including the long - term evolution (LTE (registered trademark)) advanced system, and orthogonal frequency - division multiple - access (OFDMA) systems.

[0004]

[0004] Generally, a wireless multi - connection communication system can support communication for multiple wireless terminals simultaneously. Each terminal communicates with one or more base stations via transmissions on the forward link and the reverse link. The forward link (or downlink) refers to the communication link from the base station to the terminal, and the reverse link (or uplink) refers to the communication link from the terminal to the base station. This communication link can be established via a single - input single - output, multiple - input single - output, or multiple - input multiple - output (MIMO) system.

[0005]

[0005] A wireless communication network can include several base stations that can support the communication of several wireless devices. The wireless devices can include user equipment (UE). Some UEs can be regarded as machine - type communication (MTC) UEs that can communicate with a base station, another remote device, or some other entity, and can include a remote device. Machine - type communication (MTC) can refer to communication involving at least one remote device on at least one end of the communication, and can include forms of data communication involving one or more entities that do not necessarily require human interaction. MTC UEs can include, for example, UEs that are capable of MTC communication with an MTC server and / or other MTC devices via a public land mobile network (PLMN).

Summary of the Invention

[0006]

[0006] The systems, methods, and devices of the present disclosure each have several aspects, and no single aspect among them alone bears its desirable attributes. Next, some features will be briefly described without limiting the scope of the present disclosure as represented by the following claims. After considering this description, especially after reading the section entitled "Detailed Description of the Invention", 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.

[0007] Techniques and apparatus for random access procedures and / or prioritization of broadcast transmissions in Machine Type Communication (MTC) and Extended MTC (eMTC) are provided herein. MTC / eMTC devices include devices such as sensors, meters, monitors, location tags, drones, trackers, robot / robotic devices, etc. 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). To improve the coverage of some devices, such as MTC devices, some transmissions may be sent as a bundle of transmissions, e.g., "bundling" may be utilized where the same information is transmitted on multiple subframes. Some aspects of the present disclosure relate to determining resources and / or bundling sizes for messages exchanged during random access procedures.

[0008]

[0008] Some 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 bundled Random Access Channel (RACH) messages to a Base Station (BS), determining at least one narrowband region for transmitting the RACH messages within the plurality of subframes, and determining a bundling size for the RACH messages. The bundling size indicates the number of the plurality of subframes in which the RACH messages are transmitted. The method also includes transmitting the RACH messages in the narrowband regions of the plurality of subframes, at least partially based on the determined bundling size.

[0009]

[0009] Some aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes means for determining a plurality of subframes in which the apparatus can transmit bundled RACH messages to a BS, means for determining at least one narrowband region for transmitting the RACH messages within the plurality of subframes, and means for determining a bundling size for the RACH messages. The bundling size indicates the number of subframes in which the RACH messages are transmitted. The apparatus also includes means for transmitting the RACH messages in the narrowband regions of the plurality of subframes, at least partially based on the determined bundling size.

[0010]

[0010] Some 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 bundled RACH messages to a BS, determine at least one narrowband region for transmitting the RACH messages within the plurality of subframes, and determine a bundling size for the RACH messages. The bundling size indicates the number of subframes in which the RACH messages are transmitted. The apparatus may also include a transmitter configured to transmit the RACH messages in the narrowband regions of the plurality of subframes, at least partially based on the determined bundling size. The apparatus may further include a memory coupled to the at least one processor.

[0011]

[0011] Some aspects of the present disclosure provide a computer-readable medium storing computer-executable code. The computer-executable code generally includes code for determining a plurality of subframes in which a UE may transmit a bundled RACH message to a BS, code for determining at least one narrowband region for transmitting the RACH message within the plurality of subframes, and code for determining a bundling size for the RACH message. The bundling size indicates the number of subframes in which the RACH message is transmitted. The computer-executable code also includes code for transmitting the RACH message in the narrowband regions of the plurality of subframes, at least partially based on the determined bundling size.

[0012]

[0012] Some 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 for receiving the RACH message within the plurality of subframes, and determining a bundling size for the RACH message. The bundling size indicates the number of subframes in which the RACH message is transmitted by the UE. The method also includes receiving the RACH message in the narrowband regions of the plurality of subframes, at least partially based on the determined bundling size.

[0013]

[0013] Some aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes means for determining a plurality of subframes in which a UE may transmit a bundled RACH message to the apparatus, means for determining at least one narrowband region for receiving the RACH message within the plurality of subframes, and means for determining a bundling size for the RACH message. The bundling size indicates the number of subframes in which the RACH message is transmitted by the UE. The apparatus also includes means for receiving the RACH message in the narrowband region of the plurality of subframes, at least partially based on the determined bundling size.

[0014]

[0014] Some 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 for receiving the RACH message within the plurality of subframes, and determine a bundling size for the RACH message. The bundling size indicates the number 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, at least partially based on the determined bundling size. The apparatus may further include a memory coupled to the at least one processor.

[0015]

[0015] Some aspects of the present disclosure provide a computer-readable medium storing computer-executable code. The computer-executable code generally includes code for determining a plurality of subframes in which a UE may transmit a bundled RACH message to a BS, code for determining at least one narrowband region for receiving the RACH message within the plurality of subframes, and code for determining a bundling size for the RACH message. The bundling 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 regions of the plurality of subframes, at least partially based on the determined bundling size.

[0016]

[0016] Some 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 comprising the RACH preamble, determining a RAR resource for receiving a random access response (RAR) message, at least partially based on the RACH preamble, and receiving the RAR message on the RAR resource.

[0017]

[0017] Some aspects of the present disclosure provide a method for wireless communication. The method generally includes receiving a PRACH message comprising a RACH preamble and selecting a RAR resource for transmitting a RAR message, at least partially based on the RACH preamble.

[0018]

[0018] Some 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 comprising the RACH preamble, means for determining a RAR resource for receiving a RAR message based at least in part on the RACH preamble, and means for receiving the RAR message on the RAR resource.

[0019]

[0019] Some aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally includes means for receiving a PRACH message comprising the RACH preamble and means for selecting a RAR resource for transmitting a RAR message based at least in part on the RACH preamble.

[0020]

[0020] Some 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, via the transmitter, a PRACH message comprising the RACH preamble, determine a RAR resource for receiving a RAR message based at least in part on the RACH preamble, and receive, via the receiver, the RAR message on the RAR resource.

[0021]

[0021] Some 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 comprising the 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.

[0022]

[0022] Some aspects of the present disclosure provide a method for wireless communication. The method generally includes selecting a bundling size for a PRACH message, determining a PRACH resource for transmitting the PRACH message based at least in part on the bundling size, and transmitting the PRACH message using the PRACH resource.

[0023]

[0023] In some aspects, the PRACH resource may include a narrowband frequency region of a carrier bandwidth. Determining the PRACH resource may include determining a narrowband frequency region from a set of narrowband frequency regions based at least in part on the bundling size. The method may also include identifying a set of narrowband frequency regions from a system information broadcast message. The method may further include selecting a RACH preamble, where the PRACH resource is determined independently of the RACH preamble and where the PRACH message comprises the RACH preamble.

[0024]

[0024] In some aspects, the PRACH resource may include a RACH preamble. Determining the PRACH resource may include determining a RACH preamble from a set of RACH preambles based at least in part on the bundling size. The method may also include selecting a narrowband frequency region of a carrier bandwidth for transmitting the PRACH message independently of the RACH preamble. Optionally, determining the RACH preamble may include randomly selecting a RACH preamble from a set of RACH preambles.

[0025]

[0025] The method may also include determining a start transmission time for the PRACH message based at least in part on the bundling size. Determining the start transmission time may include randomly selecting a start transmission time from a set of start transmission times.

[0026]

[0026] This method may further include selecting a transmission power for a PRACH message. The PRACH resource may be determined at least in part based on the selected transmission power.

[0027]

[0027] Some 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 at least in part based on the first PRACH resource utilized for the PRACH message. The first or second PRACH message may include at least one of a RACH preamble, a PRACH message bundling size, a narrowband frequency resource, or a start transmission time.

[0028]

[0028] Numerous other aspects are provided including methods, apparatuses, systems, computer program products, computer-readable media, and processing systems. To achieve the above and related objectives, one or more aspects comprise the features that are fully described below and particularly pointed out in the claims. The following description and the accompanying drawings detail some exemplary features of one or more aspects. However, these features are merely illustrative of some of the various ways in which the principles of the various aspects may be employed and this description is intended to embrace all such aspects and their equivalents.

[0029]

[0029] To enable a more detailed understanding of the features recited above in the present disclosure, a more specific description, briefly summarized above, can be obtained by referring to aspects, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only some exemplary aspects of the present disclosure and thus the description should not be regarded as limiting the scope of the present disclosure as other equally effective aspects may be allowed.

Brief Description of the Drawings

[0030]

Figure 1

[0030] Conceptual block diagram showing an exemplary wireless communication network according to some aspects of the present disclosure.

Figure 2

[0031] FIG. Conceptual block diagram showing an example of an evolved Node B (eNB) communicating with a user equipment (UE) in a wireless communication network according to some aspects of the present disclosure.

Figure 3

[0032] FIG. Conceptual block diagram showing an exemplary frame structure of a specific radio access technology (RAT) for use in a wireless communication network according to some aspects of the present disclosure.

Figure 4

[0033] FIG. Diagram showing an exemplary subframe format for the downlink with a normal cyclic prefix according to some aspects of the present disclosure.

Figure 5A

[0034] FIG. Diagram showing an example of machine type communication (MTC) coexistence within a broadband system such as Long Term Evolution (LTE) according to some aspects of the present disclosure.

Figure 5B

Figure 6

[0035] FIG. Diagram showing an exemplary operation for wireless communication by a UE according to some aspects of the present disclosure.

Figure 7

[0036] FIG. Diagram showing an exemplary operation for wireless communication by a BS according to some aspects of the present disclosure.

Figure 8

[0037] FIG. Diagram showing an example of a call flow for random access procedures in MTC and / or eMTC.

DETAILED DESCRIPTION OF THE INVENTION

[0031]

[0038] For ease of understanding, the same reference numbers are used, where possible, to designate the same elements that are common to each figure. It is contemplated that elements disclosed in one embodiment may be beneficially utilized with respect to other embodiments without further recitation.

[0032]

[0039] Aspects of the present disclosure provide random access procedures that may 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 may enable MTC and / or eMTC devices 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 random access procedures. Also as will be described in more detail below, the aspects presented herein may also provide techniques for prioritizing broadcast transmissions in MTC and / or eMTC.

[0033]

[0040] 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 may coexist with other legacy devices in a particular radio access technology (RAT) (e.g., Long Term Evolution (LTE), etc.) and may operate on one or more narrowband regions partitioned from the available system bandwidth supported by the particular RAT. Low-cost MTC devices may also support various operating modes, such as a coverage extension mode (e.g., where repetitions of the same message may be bundled or transmitted over multiple subframes), a normal coverage mode (e.g., where repetitions may not be transmitted).

[0034]

[0041] The techniques described herein can be used in 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. CDMA networks can implement wireless technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes wideband CDMA (W-CDMA (registered trademark)), time division synchronous CDMA (TD-SCDMA), and other variants of CDMA. cdma2000 covers the IS-2000, IS-95, and IS-856 standards. TDMA networks can implement wireless technologies such as the Global System for Mobile Communications (GSM (registered trademark)). OFDMA networks can implement wireless technologies such as evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi (registered trademark)), IEEE802.16 (WiMAX (registered trademark)), IEEE802.20, Flash-OFDM (registered trademark), etc. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) in both frequency division duplexing (FDD) and time division duplexing (TDD) use E-UTRA which utilizes OFDMA on the downlink and SC-FDMA on the uplink, and is a new release of UMTS. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from a group called the "3rd Generation Partnership Project" (3GPP). cdma2000 and UMB are described in documents from a group called the "3rd Generation Partnership Project 2" (3GPP2). The techniques described herein can be used for the above wireless networks and wireless technologies, as well as other wireless networks and wireless technologies.For clarity, some aspects of the techniques are described below with respect to LTE / LTE-A, and LTE / LTE-A terminology is used in most of the following descriptions. LTE and LTE-A are generally referred to as LTE.

[0035]

[0042] FIG. 1 shows an exemplary wireless communication network 100 having a base station (BS) and user equipment (UE) in which aspects of the present disclosure may be practiced. 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 random access procedures to initiate communication with one or more BSs in the wireless communication network, as described in more detail below.

[0036]

[0043] According to the techniques presented herein, the eNB 110 and UE 120 in the wireless communication network 100 can determine (and / or adapt) for each of the bundled messages used in the random access procedure, the location of the bundled message (e.g., one or more narrowband regions from among the available system bandwidths that can be used for the bundled message), the timing (e.g., one or more subframes that can be used for the bundled message), and / or the size (e.g., the number of one or more subframes that can be used for the bundled message). Also, according to various aspects, one or more broadcast transmissions in MTC and / or eMTC that can be utilized in the wireless communication network 100 can be prioritized according to the techniques presented herein.

[0037]

[0044] The wireless communication network 100 can be an LTE network or some other wireless network. The wireless communication network 100 can include several evolved Node Bs (eNBs) 110 and other network entities. An eNB is an entity that communicates with user equipment (UE), and may also be referred to as a base station, Node B, access point (AP), etc. Each eNB can provide communication coverage for a specific geographical area. In 3GPP, the term "cell" may refer to the coverage area of an eNB and / or the eNB subsystem serving this coverage area, depending on the context in which this term is used.

[0038]

[0045] An eNB can provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell can cover a relatively large geographical area (e.g., several kilometers in radius) and enable unrestricted access by UEs subscribed to the service. A pico cell can cover a relatively small geographical area and enable unrestricted access by UEs subscribed to the service. A femto cell can cover a relatively small geographical area (e.g., a home) and enable 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 sometimes be called a macro eNB. An eNB for a pico cell may sometimes be called a pico eNB. An eNB for a femto cell may sometimes be called a femto eNB or a Home eNB (HeNB). In the example shown in FIG. 1, eNB 110a can be a macro eNB for macro cell 102a, eNB 110b can be a pico eNB for pico cell 102b, and eNB 110c can be a femto eNB for femto cell 102c. An eNB can support one or more (e.g., three) cells. The terms "eNB", "base station", and "cell" may be used interchangeably in this specification.

[0039]

[0046] Wireless communication network 100 may also include relay stations. A relay station is an entity that can receive the transmission of data from an upstream station (e.g., eNB or UE) and send the transmission of that data to a downstream station (e.g., UE or eNB). A relay station can also be a UE that can relay transmissions to other UEs. In the example shown in FIG. 1, relay eNB 110d can communicate with macro eNB 110a and UE 120d to enable communication between eNB 110a and UE 120d. Relay stations may also be referred to as relay eNBs, relay base stations, relays, etc.

[0040]

[0047] Wireless communication network 100 can be a heterogeneous network that includes various types of eNBs, such as macro eNBs, pico eNBs, femto eNBs, relay eNBs, etc. These different types of eNBs can have different transmission power levels, different coverage areas, and different impacts on interference in wireless network 100. For example, a macro eNB can have a high transmission power level (e.g., 5 - 40 W), while pico eNBs, femto eNBs, and relay eNBs can have lower transmission power levels (e.g., 0.1 - 2 W).

[0041]

[0048] Network controller 130 can be coupled to a set of eNBs and can coordinate and control these eNBs. Network controller 130 can communicate with the eNBs via a backhaul. The eNBs can also communicate with each other directly or indirectly, for example, via a wireless backhaul or a wireline backhaul.

[0042]

[0049] UE 120 (e.g., 120a, 120b, 120c) can be distributed throughout the wireless communication network 100, and each UE can be fixed or mobile. The UE may also be referred to as an access terminal, a terminal, a mobile station (MS), a subscriber unit, a station (STA), etc. The UE can 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, a smartphone, a netbook, a smartbook, an ultrabook, an entertainment device (e.g., a music player, a game device, etc.), a camera, a mobile device, a navigation device, a drone, a robot / robotic device, a wearable device (e.g., a smartwatch, smart clothing, a smart wristband, a smart ring, a smart bracelet, smart glasses, virtual reality goggles), etc.

[0043]

[0050] One or more UEs 120 in the wireless communication network 100 (e.g., an LTE network) can also be low-cost, low data rate devices such as, for example, low-cost MTC UEs, low-cost eMTC UEs. The low-cost UEs can coexist with legacy and / or advanced UEs in the LTE network and can have one or more limited capabilities compared to other UEs (e.g., non-low-cost UEs) in the wireless network. For example, compared to legacy and / or advanced UEs in the LTE network, the low-cost UEs can operate with one or more of a reduction in maximum bandwidth (for legacy 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 collectively referred to as low-cost UEs. Similarly, legacy devices such as legacy and / or advanced (e.g., in LTE) UEs are collectively referred to as non-low-cost UEs.

[0044]

[0051] As described above, one or more UEs 120 in a wireless communication system may use random access procedures to initiate communication with an eNB 110. Random access procedures may generally be used in various situations, such as initial access from a disconnected state or radio failure, handovers that require random access procedures, downlink or uplink data arrivals during a connected state where the UE 120 subsequently loses synchronization, uplink data arrivals without an available dedicated scheduling request channel, and / or various other situations. Examples of random access procedures may include contention-based random access procedures that may be initiated on a random access channel (RACH), and contention-free (e.g., non-contention-based) random access procedures. The difference between these two procedures may be whether there is a possibility of failure using overlapping random access preambles.

[0045]

[0052] Also as described above, according to some aspects, random access procedures may also be used in MTC and / or eMTC that may coexist with LTE in a wireless communication network 100. However, as will be described in more detail, due in part to support for narrowband operation and / or banding in MTC and eMTC, the random access procedures used by one or more low-cost UEs 120 in MTC and / or eMTC may be different from the random access procedures used by non-low-cost UEs. Accordingly, the aspects presented herein provide techniques for random access procedures that may be utilized by low-cost UEs 120 in MTC and / or eMTC.

[0046]

[0053] FIG. 2 is a block diagram of the design of a BS / eNB 110 and a UE 120, which may be one of the BS / eNBs 110 and one of the UEs 120, respectively, in FIG. 1. The BS 110 may be equipped with T antennas 234a - 234t, and the UE 120 may be equipped with R antennas 252a - 252r, where generally T ≧ 1 and R ≧ 1.

[0047]

[0054] In BS110, the transmission processor 220 receives data from the data source 212 for one or more UEs, selects one or more modulation and coding schemes (MCSs) for each UE based on the channel quality indicator (CQI) received from the UE, processes (e.g., encodes and modulates) the data for each UE based on the MCS selected for that UE, and may provide data symbols for all UEs. The transmission processor 220 may also process system information and control information (e.g., CQI requests, grants, higher layer signaling, etc.) (for, e.g., semi-static resource partitioning information (SRPI)), and may provide overhead symbols and control symbols. The processor 220 may also generate reference symbols for reference signals (e.g., common reference signal (CRS)) as well as synchronization signals (e.g., primary synchronization signal (PSS) and secondary synchronization signal (SSS)). The transmit (TX) multiple input multiple output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, control symbols, overhead symbols, and / or reference symbols, if applicable, and may provide T output symbol streams to T modulators (MOD) 232a - 232t. Each MOD232 may process its respective output symbol stream (for, e.g., OFDM) to obtain an output sample stream. Each MOD232 may further process the output sample stream (e.g., analog conversion, amplification, filtering, and upconversion) to obtain a downlink signal. The T downlink signals from the modulators 232a - 232t may each be transmitted via one of the T antennas 234a - 234t.

[0048]

[0055] In UE120, antennas 252a to 252r can receive downlink signals from BS110 and / or other BSs, and can supply the received signals to respective demodulators (DEMOD) 254a to 254r. Each DEMOD 254 can condition (e.g., filter, amplify, down-convert, and digitize) its received signal to obtain input samples. Each DEMOD 254 can further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. The MIMO detector 256 can obtain received symbols from all R demodulators 254a to 254r, and, when applicable, perform MIMO detection on the received symbols to provide detected symbols. The receive processor 258 can process the detected symbols (e.g., demodulate and decode), provide decoded data for UE120 to the data sink 260, and provide decoded control signals and system information to the controller / processor 280. The channel processor can determine the reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), CQI, etc.

[0049]

[0056] On the uplink, at UE 120, transmission processor 264 may receive and process data from data source 262 and control information from controller / processor 280 (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, etc.). Processor 264 may also generate reference symbols for one or more reference signals. Symbols from transmission processor 264 may be precoded by TX MIMO processor 266, if applicable, and further processed by MOD254a - 254r (e.g., for SC - FDM, OFDM, etc.) and transmitted to BS 110. At BS 110, uplink signals from UE 120 and other UEs may be received by antenna 234, processed by DEMOD232, detected by MIMO detector 236, if applicable, and further processed by reception processor 238 to obtain the decoded data and control information sent by UE 120. Processor 238 may provide the decoded data to data sink 239 and the decoded control information to controller / processor 240. BS 110 may include communication unit 244 and communicate with network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller / processor 290, and memory 292.

[0050]

[0057] Controllers / processors 240 and 280 can respectively instruct operations in BS110 and UE120. For example, the controller / processor 240 and / or other processors and modules in BS110 can implement or instruct the operations 700 shown in FIG. 7 and / or other processes for the techniques described herein. Similarly, the controller / processor 280 and / or other processors and modules in UE120 can implement or instruct the operations 600 shown in FIG. 6 and / or processes for the techniques described herein. Memories 242 and 282 can respectively store data and program code for BS110 and UE120. Scheduler 246 can schedule the UE for data transmission on the downlink and / or uplink.

[0051]

[0058] FIG. 3 shows an exemplary frame structure 300 for FDD in LTE. Each transmission timeline for the downlink and uplink can be divided into units of radio frames. Each radio frame can have a predetermined duration (e.g., 10 milliseconds (ms)) and can be divided into 10 subframes with indices from 0 to 9. Each subframe can include two slots. Thus, each radio frame can include 20 slots with indices from 0 to 19. Each slot can include L symbol periods, e.g., 7 symbol periods in the case of a normal cyclic prefix (as shown in FIG. 2) or 6 symbol periods in the case of an extended cyclic prefix. The 2L symbol periods in each subframe can be assigned indices from 0 to 2L - 1.

[0052]

[0059] In LTE, the eNB may transmit the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) on the downlink at 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 during subframes 0 and 5 of each radio frame with a normal cyclic prefix, as shown in FIG. 3. The PSS and SSS may be used by the UE for cell search and acquisition. The eNB may transmit cell-specific reference signals (CRS) across the system bandwidth for each cell supported by the eNB. The CRS may be transmitted during some symbol periods of each subframe and may be used by the UE to perform channel estimation, channel quality measurement, and / or other functions. The eNB may also transmit the physical broadcast channel (PBCH) during symbol periods 0 to 3 in slot 1 of some radio frames. The PBCH may carry some system information. The eNB may transmit other system information such as system information blocks (SIBs) on the physical downlink shared channel (PDSCH) in some subframes. The eNB may transmit control information / data on the physical downlink control channel (PDCCH) during the first B symbol periods of the subframe, where B may be configurable for each subframe. The eNB may transmit traffic data and / or other data on the PDSCH during the remaining symbol periods of each subframe.

[0053]

[0060] The PSS, SSS, CRS, and PBCH in LTE are described in 3GPP TS 36.211 entitled "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation", which is publicly available.

[0054]

[0061] Figure 4 shows two exemplary subframe formats 410 and 420 for the downlink with a normal cyclic prefix. The available time-frequency resources for the downlink can be partitioned into resource blocks. Each resource block may cover 12 subcarriers in one slot and may include several resource elements. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol which can be a real-valued or complex-valued number.

[0055]

[0062] Subframe format 410 may be used for an eNB equipped with two antennas. The CRS may be transmitted from antennas 0 and 1 during symbol periods 0, 4, 7, and 11. A reference signal is a signal that is known a priori by the transmitter and the receiver and may also be called a pilot. The CRS is a cell-specific reference signal generated, for example, based on the cell identification information (ID). In Figure 4, for a given resource element with label Ra, a modulation symbol may be transmitted from antenna a on that resource element, and modulation symbols may not be transmitted from other antennas on that resource element. Subframe format 420 may be used for an eNB equipped with four antennas. The CRS may be transmitted from antennas 0 and 1 during symbol periods 0, 4, 7, and 11, and may be transmitted from antennas 2 and 3 during symbol periods 1 and 8. For both subframe formats 410 and 420, the CRS may be transmitted on evenly spaced subcarriers that may be determined based on the cell ID. Different eNBs may transmit their CRSs on the same or different subcarriers depending on their cell IDs. For both subframe formats 410 and 420, the resource elements not used for the CRS may be used to transmit data (e.g., traffic data, control data, and / or other data).

[0056]

[0063] An interleaving structure can be used for each of the downlink and uplink for FDD in LTE. For example, Q interleaves with indices from 0 to Q - 1 can be defined, where Q can be equal to 4, 6, 8, 10, or some other value. Each interleave can include subframes separated by only Q frames. In particular, interleave q can include subframes q, q + Q, q + 2Q, etc., where q ∈ {0,..., Q - 1}.

[0057]

[0064] The wireless network may support hybrid automatic repeat request (HARQ) for data transmission in the downlink and uplink. In the case of HARQ, a transmitter (e.g., eNB 110) can send one or more transmission signals of its packet until the packet is correctly decoded by a receiver (e.g., UE 120) or until some other end condition is encountered. In the case of synchronous HARQ, all transmissions of a packet can be sent within the subframes of a single interleave. In the case of asynchronous HARQ, each transmission of a packet can be sent within any subframe.

[0058]

[0065] A UE can be located within the coverage of multiple eNBs. To serve that UE, one of these eNBs can be selected. The serving eNB can be selected based on various criteria such as received signal strength, received signal quality, path loss, etc. The received signal quality can be quantified by the signal-to-interference-plus-noise ratio (SINR), or the reference signal received quality (RSRQ), or some other metric. The UE can operate in a dominant interference scenario where the UE can observe high interference from one or more interfering eNBs.

[0059]

[0066] As described above, one or more UEs in a wireless communication network (e.g., wireless communication network 100) can be devices with limited communication resources, such as low-cost UEs, compared to other (non-low-cost) devices in the wireless communication network.

[0060]

[0067] In some systems, for example, in LTE Rel-13, low-cost UEs may be limited to specific narrowband allocations within the available system bandwidth (e.g., of six or fewer resource blocks (RBs)). However, low-cost UEs may be able to retune (e.g., operate and / or camp) to different narrowband regions within the available system bandwidth of the LTE system in order to coexist, for example, within the LTE system.

[0061]

[0068] As another example of coexistence within the LTE system, a low-cost UE may be able to receive (repeatedly) a legacy physical broadcast channel (PBCH) (e.g., an LTE physical channel that carries parameters that may generally 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 may be able to receive a legacy PBCH with one or more additional repetitions of the PBCH over a plurality of subframes. As another example, a low-cost UE may be able to transmit to an eNB (e.g., eNB 110) in the LTE system one or more repetitions of a PRACH (e.g., having one or more PRACH formats that are supported). The PRACH may be used to identify the low-cost UE. Also, the number of repeated PRACH attempts may be configured by the eNB.

[0062]

[0069] The low-cost UE can also be a link budget-limited device and can operate in different operating modes based on its link budget limitation (e.g., using a different number of repetitions for messages transmitted to or from the low-cost UE). For example, in some cases, the low-cost UE can operate in a normal coverage mode with few to no repetitions (e.g., the amount of repetitions required for the UE to successfully receive and / or transmit a message can be low or even unnecessary). Alternatively, in some cases, the low-cost UE can operate in a coverage extension (CE) mode with a high amount of repetitions. For example, for a 328-bit payload, the low-cost UE in CE mode may require 150 or more repetitions of the payload to successfully transmit and / or receive the payload.

[0063]

[0070] In some cases, for example, in LTE Rel-13, the low-cost UE may have limited capabilities with respect to its reception of broadcast transmissions and unicast transmissions (e.g., for system information blocks (SIBs), paging messages, random access response (RAR) messages, etc.). For example, the maximum transport block (TB) size for broadcast transmissions received by the low-cost UE can be limited to 1000 bits. Further, in some cases, the low-cost UE may be unable to receive two or more unicast TBs in a subframe. In some cases (e.g., for both the CE mode and the normal mode described above), the low-cost UE may be unable to receive two or more broadcast TBs in a subframe. Further, in some cases, the low-cost UE may be unable to receive both a unicast TB and a broadcast TB in a subframe.

[0064]

[0071] In MTC, low-cost UEs coexisting in an LTE system may also support new messages for several procedures, such as paging, random access procedures, reception of broadcast system information, etc. (e.g., as opposed to the conventional messages used in LTE for these procedures). In other words, these new messages for paging, random access procedures, etc. may be separate from the messages used for similar procedures related to non-low-cost UEs. For example, compared to the conventional paging messages used in LTE, a low-cost UE may be able to monitor and / or receive paging messages that may be impossible for non-low-cost UEs to monitor and / or receive. Similarly, compared to the conventional RAR messages used in conventional random access procedures, a low-cost UE may be able to receive RAR messages that may be impossible for non-low-cost UEs to receive. The new paging and RAR messages related to low-cost UEs may also be repeated one or more times (e.g., bundled). Furthermore, different numbers of repetitions (e.g., different bundling sizes) for the new messages may be supported.

[0065] Exemplary MTC Coexistence within a Wideband System

[0072] As described above, MTC and / or eMTC operation may be supported in a wireless communication network (e.g., wireless communication network 100) (e.g., in coexistence with LTE or some other RAT). FIGS. 5A and 5B show, for example, an example of how a low-cost UE in MTC operation may coexist within a wideband system such as LTE.

[0066]

[0073] As shown in the exemplary frame structure 500A of FIG. 5A, subframes 502 related to MTC and / or eMTC operations can be time-division multiplexed (TDM) with normal subframes 504 related to LTE (or some other RAT). As shown in the illustration, in one exemplary implementation, the number of subframes 502 related to (e)MTC operations can be relatively small compared to the number of normal subframes 504.

[0067]

[0074] Additionally or alternatively, as shown in the exemplary frame structure of subframe 500B in FIG. 5B, one or more narrow bands used by low-cost UEs in MTC can be frequency-division multiplexed (FDM) within a wider bandwidth supported by LTE. Multiple narrow-band regions can be supported for MTC and / or eMTC operations, and each narrow-band region spans a bandwidth of six resource blocks (RBs) or less. In some cases, each low-cost UE in MTC operations can operate within one narrow-band region at a time (e.g., at 1.4 MHz or in six RBs). However, a low-cost UE in MTC operations can re-tune to other narrow-band regions within the wider system bandwidth at a given time. In some examples, multiple low-cost UEs can be served by the same narrow-band region. In other examples, multiple low-cost UEs can be served by different narrow-band regions (e.g., where each narrow-band region spans six RBs). In yet other examples, different combinations of low-cost UEs can be served by one or more of the same narrow-band regions and / or one or more different narrow-band regions.

[0068]

[0075] As shown in FIG. 5B, in subframe 500B, a low-cost UE can monitor the wideband region 506 for legacy control information and monitor the wideband regions 508A and 508B for data. The low-cost UE can operate (e.g., monitor / receive / transmit) for various different operations within the narrowband region. For example, as shown in FIG. 5B, the first narrowband region 510 of the subframe (e.g., spanning six or fewer RBs) can be monitored by one or more low-cost UEs for any of the following in a wireless communication network: a primary synchronization signal (PSS) from the BS, a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), MTC signaling, or paging transmission. Also as shown in FIG. 5B, the low-cost UE can retune to a second narrowband region 512 of the subframe (e.g., also spanning six or fewer RBs) to transmit previously configured RACH or data during signaling received from the BS. In some cases, the second narrowband region 512 can be utilized by the same low-cost UE that utilized the first narrowband region 510 (e.g., the low-cost UE may retune to the second narrowband region to transmit after monitoring in the first narrowband region). In some cases (not shown), the second narrowband region 512 can be utilized by a low-cost UE different from the low-cost UE that utilized the first narrowband region 510.

[0069]

[0076] Those skilled in the art will recognize that the techniques presented herein can be applied to narrowband regions of different sizes, although the examples described herein assume a narrowband of six RBs.

[0070] Exemplary Random Access Procedures for eMTC

[0077] As described above, in some systems (e.g., LTE Rel-13 systems), narrowband operation for eMTC may be supported. Further, as also described above, different operating modes for low-cost devices such as low-cost UEs in eMTC may be supported, where different amounts of repetition may be used before a message is successfully received and / or transmitted by a low-cost UE.

[0071]

[0078] According to some aspects, the random access procedures in MTC and / or eMTC may also use narrowband operation and different amounts of bundling for different messages used in the random access procedure. For example, as shown in FIG. 8, a low-cost UE and / or eNB in eMTC may use bundled (e.g., one or more repetitions) random access channel (RACH) preambles (MTC_MSG1), bundled random access response (RAR) messages (MTC_MSG2), bundled connection request messages (MTC_MSG3), and / or bundled contention resolution messages (MTC_MSG4) in the random access procedure (e.g., monitor / transmit / receive). Further, each of the bundled messages used in the random access procedure may be transmitted / received in multiple subframes and in one or more narrowbands partitioned from the available system bandwidth. Further, the bundling size (e.g., the number of multiple subframes in which each of the bundled messages is transmitted) of each of the bundled messages may vary.

[0072]

[0079] Thus, in some situations, support for these features may be useful for the BS and / or low-cost UE to know the specific manner (e.g., location, timing, and amount) in which each of the bundled messages used in the random access procedure is transmitted / received.

[0073]

[0080] Accordingly, as described above, the aspects presented in this specification enable low-cost UEs and BSs to determine (and / or adapt) for each of the bundled messages used in the random access procedure, the location of the bundled message (e.g., one or more narrowband regions from within the available system bandwidth that can be used for the bundled message), the timing (e.g., one or more subframes that can be used for the bundled message), and / or the size (e.g., the number of one or more subframes that can be used for the bundled message).

[0074]

[0081] FIG. 6 shows an exemplary operation 600 for wireless communication according to some aspects of the present disclosure. Operation 600 may be performed by a UE, such as a low-cost UE, that may be one of the UEs 120 shown in FIGS. 1 and 2.

[0075]

[0082] Operation 600 may begin at 602, where the UE determines a plurality of subframes in which the UE can transmit the bundled RACH message to the BS. At 604, the UE determines at least one narrowband region within the subframe for transmitting the RACH message. At 606, the UE determines a bundling size for the RACH message, where the bundling size indicates the number of subframes in which the RACH message is transmitted. At 608, the UE transmits the RACH message in the narrowband regions of the plurality of subframes based at least in part on the determined bundling size.

[0076]

[0083] FIG. 7 shows an exemplary operation 700 for wireless communication according to some aspects of the present disclosure. Operation 700 may be performed by a BS, such as one of the BS / eNBs 110 shown in FIGS. 1 and 2.

[0077]

[0084] Operation 700 may start at 702, where the BS determines a plurality of subframes in which a bundled RACH message can be sent by the UE (e.g., a low-cost UE) to the BS. At 704, the BS determines at least one narrowband region within the subframe for receiving the RACH message. At 706, the BS determines a bundling size for the RACH message, where the bundling size indicates the number of subframes in which the RACH message is sent by the UE. At 708, the BS receives the RACH message in the narrowband regions of the plurality of subframes, at least partially based on the determined bundling size.

[0078]

[0085] FIG. 8 shows an example of a call flow 800 for a random access procedure in MTC and / or eMTC. The eNB and MTC device (e.g., a low-cost UE) shown in FIG. 8 can be, for example, any of the BS / eNB 110 and UE 120 shown in FIGS. 1-2, respectively.

[0079]

[0086] In one reference example of a random access procedure (in MTC, eMTC, etc.), at 802, UE 120 transmits a bundled RACH preamble (e.g., MTC_MSG1) to eNB 110 (e.g., to initiate communication with the eNB). The UE may select a RACH preamble for a RACH message from a set of RACH preambles. The UE may transmit a bundled RACH message (including the selected RACH preamble) to the eNB. According to some aspects, UE 120 transmits to eNB 110 a RACH message bundled with one or more different bundling sizes (e.g., bundling sizes of 1, 2, 3, etc.). For example, in some cases, the amount of bundling used for the bundled RACH message may be at least partially based on the particular coverage mode (e.g., CE mode, normal mode, etc.) in which UE 120 is operating. As described above, when UE 120 is operating in the normal mode, UE 120 may use a lower amount of bundling compared to the amount of bundling used when UE 120 is operating in the CE mode. Generally, however, UE 120 and / or eNB 110 may support multiple bundling sizes for different coverage extensions.

[0080]

[0087] Accordingly, the aspects presented herein provide techniques that enable UE 120 and / or eNB 110 to determine a bundling size for a bundled RACH message transmitted to eNB 110 in a random access procedure. In one aspect, UE 120 and / or eNB 110 may determine a bundling size for a bundled RACH message at least partially based on broadcast signaling from eNB 110. As described above, the broadcast signaling used to indicate the bundling size may be broadcast signaling that is separate from the broadcast signaling used to indicate system information to non-low-cost UEs.

[0081]

[0088] According to some aspects, UE120 and / or eNB110 may determine a bundling size for bundled RACH messages based at least in part on the location of one or more narrowband regions partitioned from the available system bandwidth. For example, in some cases, each of the one or more narrowband regions may have a fixed bundling size that can be used for RACH transmission. In some cases, each of the narrowband regions may have a different fixed bundling size for RACH transmission. In some cases, one or more narrowband regions may have the same fixed bundling size as one or more other narrowband regions.

[0082]

[0089] In some aspects, one or more narrowband regions may support different coverage modes for UE120, and the bundling size for RACH transmission may be determined based at least in part on one or more narrowband regions that support a particular coverage mode for UE120. For example, in some cases, when UE120 is operating in a normal coverage mode, UE120 may identify one or more narrowband regions that support its normal coverage mode. UE120 may then determine the bundling size for RACH transmission based at least in part on, for example, the fixed bundling size used by one or more narrowband regions that support the normal coverage mode. Similar examples may apply to the CE mode and / or other modes of UE120.

[0083]

[0090] According to some aspects, UE120 and / or eNB110 may determine a bundling size for the bundled RACH message based at least in part on the starting subframe of the bundled RACH message. For example, within each of one or more narrowband regions, multiple bundling sizes may be supported. In some cases, within a particular narrowband region, a first set of subframes may have a particular bundling size for RACH transmissions, and a second set of subframes may have another bundling size for other transmissions. In these cases, within each of one or more narrowband regions, the bundling size used for the bundled RACH transmission may vary according to the subframe in which the bundled RACH transmission may start therein (e.g., in the first set of subframes).

[0084]

[0091] According to some aspects, UE120 and / or eNB110 may determine a bundling size for the bundled RACH message based at least in part on the estimated CE target of a low-cost UE (e.g., for CE mode). For example, UE120 (and / or eNB110) may identify an estimated CE target that may be used for RACH transmissions based at least in part on the quality of the radio state between UE120 and eNB110. In some cases, UE120 may use the downlink (DL) path loss to determine the estimated CE target. For example, based on the DL path loss, UE120 may determine that UE120 should operate in CE mode for the bundled RACH and use a relatively large bundling size (e.g., compared to the bundling size used for normal mode). In other examples, UE120 may determine one or more other bundling sizes for the bundled RACH (e.g., based on other quality measurements).

[0085]

[0092] According to some aspects, UE120 and / or eNB110 may determine the bundling size for the bundled RACH message based on the success or failure of eNB110 to successfully decode the previously transmitted bundled RACH message. For example, in some cases, if UE120 successfully decodes a random access response (RAR) message from eNB110 for a previously transmitted bundled RACH (e.g., MTC_MSG1), UE120 may determine the success (of eNB110 in decoding the previously transmitted bundled RACH message such as MTC_MSG1). Similarly, in some cases, UE120 may determine the failure (of eNB110 in decoding the previously transmitted bundled RACH message) if UE120 is unable to successfully decode the RAR message from eNB110 for the previously transmitted bundled RACH. In some cases (e.g., if UE120 determines failure), UE120 may increase the bundling size relative to the bundling size used for the previous bundled RACH message in response to the failure of eNB110 to successfully decode the previous bundled RACH message.

[0086]

[0093] Additionally or alternatively, in some cases, in response to the failure of eNB110 to successfully decode the previous bundled RACH message, UE120 may increase the transmission power relative to the transmission power used to transmit the previous bundled RACH message. In some aspects, the transmission power may be increased for the bundling size used for the previous bundled RACH message and / or for the bundling size used for the subsequently transmitted bundled RACH message. Further, when transmitting the bundled RACH message, the RACH counter in UE120 may be incremented only once per bundled RACH message (as opposed to being incremented for each RACH message transmitted within a single bundled RACH, for example).

[0087]

[0094] As described above, the aspects presented in this specification also provide a technique that enables the UE 120 and / or the eNB 110 to determine a plurality of subframes in which the UE 120 can transmit a bundled RACH to the eNB 110. In one aspect, the plurality of subframes can be determined at least in part based on a particular subframe available as the start subframe of the bundled RACH message.

[0088]

[0095] For example, if the UE 120 and / or the eNB 110 determines a bundling size of 4 for the bundled RACH, in some cases, each bundled RACH transmission can start in subframes 0, 4, 8, etc. (e.g., here, each RACH transmission of the bundled RACH is performed in consecutive subframes). In another case, for example, using the same bundling size of 4 for the bundled RACH, each RACH transmission of the bundled RACH transmission can start in subframes 0, 2, 4, 6, etc. (e.g., here, each RACH transmission of the bundled RACH is performed in non-consecutive subframes). Generally, however, the determination of the start subframe for each bundled RACH transmission can be at least in part based on the particular subframe uplink / downlink configuration used in the frame.

[0089]

[0096] As shown in FIG. 8, 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_MSG2) to UE 120. The UE determines a RAR resource for receiving the RAR message based at least in part on the RACH preamble, and receives the RAR message on that RAR resource. The RAR resource may include at least one of a narrowband frequency region of the carrier bandwidth, a start transmission time, a start subframe, or a bundling size. In some cases, the bundled RAR message may not support HARQ. As shown in FIG. 8, the bundling size for the bundled RAR message may be based at least in part on the bundled RACH message.

[0090]

[0097] 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 one or more control channel candidates. In some cases, identifying one or more control channel decoding candidates may include determining at least one of an aggregation level (e.g., the number of control channel elements (CCEs) and / or enhanced control channel elements (eCCEs)), the RAR message bundling size, or the 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 bundling size of the RAR message.

[0091]

[0098] In some aspects, the UE120 and / or the eNB110 may determine a bundling size and / or a narrowband region for the bundled RAR message, at least partially based on the RACH message selected by the UE. The RAR message bundling size and / or the narrowband region may further depend on at least one of the narrowband region or the bundling size of the bundled RACH message. For example, in some cases, the bundling size of the bundled RAR message may be the same as the bundling size of the bundled RACH message received from a low-cost UE (e.g., a bundling size of 4 in one implementation shown in FIG. 8). In some cases, the bundling size of the bundled RAR message may be determined from the bundling size used in one or more of the narrowband regions for transmitting the bundled RACH message. In some cases, the bundling size of the RAR message may not depend on the bundling size of the PRACH message.

[0092]

[0099] In some aspects, the control and / or data portions of the RAR message may be bundled. For example, the control portion of the RAR message may have a bundling size that is the same as or different from the bundling size used for the data portion of the RAR message. In some aspects, the bundling size and / or narrowband region for the control portion of the RAR message (e.g., on the ePDCCH) may be implicitly determined based at least in part on at least one property of each RACH message selected by the UE. For example, the determination of the narrowband region used for the control portion of the RAR message and / or the bundling size used to transmit the control portion of the RAR message may be based at least in part on the bundling size and / or narrowband region used to transmit the RACH message. In some cases, there may be a one-to-one mapping from the bundling size and / or narrowband region used for the RACH message to the bundling size and / or narrowband region used for the control portion of the RAR message.

[0093]

[0100] According to some aspects, the timing of the bundled RAR message may be based at least in part on the bundling size of the RACH message. For example, after transmitting the bundled RACH message, the UE 120 may expect the bundled RAR message within a time period following the transmission of the bundled RACH.

[0094]

[0101] In conventional random access procedures (e.g., used by non-low-cost UEs), the time period may only last for a fixed time period (e.g., about 10 ms). However, in eMTC, due to bundling, subframe configuration, etc., this time period may not be sufficient for a low-cost UE to detect whether the bundled RAR has been successfully received. For example, as described above, for partially sufficient bundling, the first subframe of the RAR (including the control portion) may need to start in a specific subframe.

[0095]

[0102] Thus, the techniques presented herein may allow for an extended time period (e.g., in eMTC) in order to allow more time for low-cost UEs to detect bundled RAR transmissions without declaring a RACH failure. In some cases, the calculations used for a random access radio network temporary identifier (RA-RNTI) that is used to handle a bundled RAR message may be different from those used in legacy random access procedures. For example, in eMTC, the RA-RNTI calculation may use the subframe in which the bundled RACH started or ended.

[0096]

[0103] In some aspects, the bundled RAR provides permission to send a connection request message. For example, the bundled RAR message may contain various amounts of information (e.g., in UL grant) that can be used by a low-cost UE when sending / receiving one or more subsequent bundled messages in a random access procedure. As shown in FIG. 8, for example, both a bundled connection request message (e.g., MTC_MSG3 at 806) and / or a bundled contention resolution message (e.g., MTC_MSG4 at 808) may be at least partially based on the bundled RAR message.

[0097]

[0104] In some cases, the bundled RAR message may indicate (via the UL grant) at least one of a narrowband region or a bundling size for the UE 120 to send a bundled connection request message (e.g., MTC_MSG3) to the eNB 110. Alternatively or additionally, in some cases, the bundled RAR message may also indicate (via the UL grant) a narrowband region or a bundling size for the UE 120 to receive a bundled contention resolution message (e.g., MTC_MSG4) from the eNB 110.

[0098]

[0105] In some aspects, the RAR grant in the bundled RAR message may be defined differently from the RAR grant used in legacy random access procedures. 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 allocation, 4 bits for a shortened modulation and coding scheme, 3 bits for a transmission / 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.

[0099]

[0106] According to some aspects, in a low-cost UE in eMTC (e.g., under TTI bundling), the RAR grant in the bundled RAR message may be 12 bits, including 2 bits for the transport block size (TBS) indicator, 4 bits for the UL resource block allocation indicator, 3 bits for the bundling length and sub-band hopping indicator, and 3 bits for the TPC mode indicator and TPC command. In some cases, the TBS indicator may indicate a 4-phase shift keying (QPSK) modulation and coding scheme (MCS). In some cases, the UL resource block allocation indicator may be used to indicate a specific resource allocation within a sub-band of 6 resource blocks (e.g., narrowband region). In some cases, the bundling length and sub-band hopping indicator may indicate a specific bundling length and sub-band hopping sequence for a given bundling length. For example, for 32 given bundling lengths, the bundling length and sub-band hopping indicator may indicate that there should be 8 blocks of the message, and each block of the message is hopped in 4 different sub-bands. 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 the maximum power mode or some other power mode. Alternatively, one or more TPC commands may be used within the RAR grant to indicate at what power the low-cost UE should transmit.

[0100]

[0107] As described above, after the eNB 110 transmits the bundled RAR message to the UE 120 at 804, the UE 120 may use various information (e.g., provided in the RAR grant defined above) in the bundled RAR message to transmit a bundled radio resource control (RRC) connection request message (e.g., MTC_MSG3) to the eNB 110 at 806. In other words, the RAR message may provide a grant for transmitting the connection request message, and this grant may indicate information about the TBS, bundling length, sub-band hopping indicator, TPC, etc. for the connection request message. In some cases, as described above, the specific narrowband region and / or bundling size of the bundled RRC connection request message may be indicated by the received bundled RAR message.

[0101]

[0108] Furthermore, some aspects presented herein may allow the transmission timing of the bundled RRC connection request message to change (e.g., as opposed to legacy random access procedures). For example, generally, in legacy random access procedures, the transmission timing for transmitting 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 need to adapt according to the amount of bundling used for the bundled RAR and the bundled connection request message.

[0102]

[0109] Accordingly, the techniques presented herein may enable the timing of transmitting the connection request message to be at least partially based on the bundling size of the bundled RAR message and / or the bundling size of the connection request message. For example, when UE120 decodes the RAR grant in the bundled RAR message in a specific subframe k, it may start transmitting the bundled connection request message on the first uplink subframe k+n, n>n1, where n1 includes the time for UE120 to prepare a new UL packet and / or perform possible narrowband retuning.

[0103]

[0110] Furthermore, in some cases, the amount of bundling used for the bundled connection request message may depend on the narrowband region in which UE120 is operating and / or the time required to retune to another narrowband region. For example, as described above, in some cases, the bundled connection request transmission may start in a specific subframe, and the bundling amount may depend on the number of available subframes remaining in the narrowband region that can be used for uplink transmission.

[0104]

[0111] After UE120 transmits the bundled connection request message to eNB110 at 806, UE120 may expect to receive a bundled contention resolution message (e.g., MTC_MSG4) from eNB110. As described above, in some cases, the narrowband region and / or bundling size used for the bundled contention resolution message may be determined at least partially based on the indication in the bundled RAR message received from eNB110. In some cases, however, if the narrowband region and / or bundling size 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 where the bundled RAR message was transmitted and / or use the same bundling size as that used by the bundled RAR message.

[0105]

[0112] The techniques described herein may be used for random access procedures in MTC and eMTC. However, those skilled in the art will understand that the techniques presented herein may also be applicable to other procedures in MTC and / or eMTC, such as paging, transmission / reception of system information, etc.

[0106] Exemplary Broadcast Transmission Prioritization for eMTC

[0113] The aspects presented herein may also provide techniques for prioritizing broadcast transmissions in MTC and / or eMTC.

[0107]

[0114] As described above, in some cases, a low-cost UE may not be able to receive more than a single broadcast TB at a given time. For example, for each subframe, a low-cost UE may be able to receive only one of, for example, a RAR message, a paging message, or broadcast signaling at a time. Further, different broadcast transmissions may be performed in different narrowband regions, but the BS may be able to broadcast transmissions simultaneously for each narrowband region at the same time. Thus, in some cases, there may be times when a low-cost UE expects a particular broadcast transmission from the BS, but the BS is not transmitting that particular broadcast transmission.

[0108]

[0115] Therefore, the techniques herein provide priority rules for a device in eMTC to follow when transmitting / receiving a broadcast transmission.

[0109]

[0116] In some aspects, the low-cost UE may apply one or more priority rules when determining the types of messages to collect from the BS (e.g., broadcast transmissions). For example, broadcast transmissions (from the BS) can be, for example, (bundled) random access responses from the BS, (bundled) paging messages, broadcast messages carrying system information, etc. In some cases, the low-cost UE may apply the priority rules after transmitting the RACH message to the BS.

[0110]

[0117] In a particular implementation, the low-cost UE defines the reception of a bundled RAR message as the first priority (e.g., since the RAR message can be triggered by the transmitted RACH), defines the reception of a paging message as the second priority (e.g., which can be used for incoming data notification and update of system information), and may define the reception of system information as the third priority (e.g., generally, it may not be necessary to receive frequently, but it may also be indicated via paging).

[0111]

[0118] Thus, in the above example, if the low-cost UE has transmitted a bundled RACH message and has not yet received the bundled RAR message from the BS, the low-cost UE may decide to monitor for the broadcast bundled RAR message before monitoring for paging messages and system information. However, if the low-cost UE has not transmitted a bundled RACH message and has not received an RAR message either, the low-cost UE may decide to monitor for the broadcast paging message before monitoring for broadcast system information, etc.

[0112]

[0119] Generally, however, in the above examples, while a specific priority for collecting broadcast transmissions from a BS in eMTC has been described, those skilled in the art will recognize that other priorities may be defined for broadcast transmissions in MTC and / or eMTC.

[0113]

[0120] As used herein, the phrase referring to "at least one of" a list of items refers to any combination of those items, including a single member. By way of example, "at least one of a, b, or c" includes a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination using multiple of the same elements (for example, a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c, or any other arrangement of a, b, and c).

[0114]

[0121] As used herein, the term "determining" encompasses a wide variety of acts. For example, "determining" can include calculating, computing, processing, deriving, investigating, looking up (for example, looking up in a table, database or another data structure), ascertaining, etc. Further, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), etc. Further, "determining" can include solving, selecting, choosing, establishing, etc.

[0115]

[0122] In some cases, rather than actually communicating the frame, the device can have an interface for communicating the frame for transmission or reception. For example, a processor can output a frame to an RF front end for transmission via a bus interface. Similarly, rather than actually receiving the frame, the device can have an interface for obtaining a frame received from another device. For example, a processor can obtain (or receive) a frame from an RF front end for transmission via a bus interface.

[0116]

[0123] The methods disclosed herein comprise one or more steps or acts for achieving the described methods. The steps and / or acts of the methods can be interchanged with each other without departing from the scope of the claims. In other words, unless a specific order of steps or acts is specified, the order and / or use of the specific steps and / or acts can be changed without departing from the scope of the claims.

[0117]

[0124] The various operations of the methods described above may be implemented by any suitable means capable of performing the corresponding functions. One or more processors, circuits, or other devices may execute software. Software should be broadly construed to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc., whether called software, firmware, middleware, microcode, a hardware description language, or by any other name. Those means may include various (one or more) hardware and / or software components and / or modules including, but not limited to, circuits, application specific integrated circuits (ASICs), or processors. Generally, where there are operations shown in the figures, those operations may be implemented by any suitable corresponding means-plus-function components.

[0118]

[0125] For example, the means for receiving and / or for monitoring may include receivers such as the receive processor 238, MIMO detector 236, demodulators 232a-232t, and / or antennas 234a-234t of the base station 110 shown in FIG. 2, and / or the MIMO detector 256, receive processor 258, demodulators 254a-254r, and / or antennas 252a-252r of the user equipment 120 shown in FIG. 2. The means for determining, monitoring means, means for applying, means for decoding, means for indicating, means for selecting, means for increasing, and / or means for implementing may include one or more processors (or processing systems) such as the controller / processor 240, scheduler 246, transmitter processor 220, receive processor 238, MIMO detector 236, TX MIMO processor 230, and / or modulator / demodulators 232a-232t of the base station 110 shown in FIG. 2, and / or the controller / processor 280, receive processor 258, transmitter processor 264, MIMO detector 256, TX MIMO processor 266, and / or modulator / demodulators 254a-254r of the user equipment 120 shown in FIG. 2. The means for signaling, means for providing, means for transmitting, means for increasing, and / or means for indicating may include transmitters such as the transmitter processor 220, TX MIMO processor 230, modulators 232a-232t, and / or antennas 234a-234t of the base station 110 shown in FIG. 2, and / or the transmitter processor 264, TX MIMO processor 266, modulators 254a-254r, and / or antennas 252a-252r of the user equipment 120 shown in FIG. 2.

[0119]

[0126] Those skilled in the art will appreciate that information and signals may be represented using any of a variety of techniques and technologies. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or combinations thereof.

[0120]

[0127] Furthermore, those skilled in the art will appreciate that the various exemplary logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein can be implemented as hardware, software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various exemplary components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in varying ways for each particular application, but such implementations should not be construed as departing from the scope of the present disclosure.

[0121]

[0128] The various exemplary logical blocks, modules, and circuits described in connection with the disclosure herein can be implemented or executed using 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 gates 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 (e.g., 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).

[0122]

[0129] The steps of the methods or algorithms described in connection with the disclosure of this specification may be implemented directly in hardware, implemented by software modules executed by a processor, or implemented in a combination thereof. The software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM (registered trademark) memory, phase change memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integrated into the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

[0123]

[0130] In one or more exemplary designs, the described functionality may be implemented in hardware, software, or a combination thereof. If implemented in software, the functionality may be stored on or transmitted over a computer-readable medium as one or more instructions or code. A computer-readable medium includes both a computer storage medium and a communication medium including any medium that facilitates transfer of a computer program from one place to another. The storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD / DVD or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general purpose or special purpose computer, or a general purpose or special purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disk generally magnetically reproduces data, and disc optically reproduces data with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0124]

[0131] The foregoing 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 readily apparent to those skilled in the art, and the general 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 accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 1. A method for wireless communication by a user equipment (UE), comprising: determining a number 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 plurality of subframes for transmitting the bundled RACH message; determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted; transmitting the bundled RACH message in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size.

2. The method of claim 1 , wherein the plurality of subframes is determined based at least in part on a particular subframe available as a starting subframe for the bundled RACH message.

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

4. 2. The method of claim 1, wherein the bundling size for the bundled RACH messages is determined based at least in part on a location or a starting subframe of the at least one narrowband region of the bundled RACH messages.

5. The method of claim 1 , wherein the bundling size for the bundled RACH messages is determined based at least in part on an estimated coverage extension target.

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

7. 7. The method of claim 6, 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 message.

8. in response to the BS's failure to successfully decode the previous bundled RACH message. increasing the bundling size for the bundled RACH message relative to a bundling size for the previous bundled RACH message; or 7. The method of claim 6, further comprising at least one of increasing a transmit power for the bundled RACH message relative to a transmit power for the previous bundled RACH message.

9. The method of claim 1 , further comprising receiving a bundled random access response message from the BS.

10. 10. The method of claim 9, wherein at least one of a narrowband region or a bundling size of the control portion of the bundled random access response message is based at least in part on a determination of at least one property from the selected bundled RACH message.

11. The method of claim 10 , wherein the at least one property comprises at least one of the at least one narrowband region or the bundling size of the bundled RACH message.

12. 10. The method of claim 9, wherein timing of the bundled random access response messages is based at least in part on the bundling size of the bundled RACH messages.

13. The method of claim 9 , wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for the UE to transmit a connection request message.

14. The method of claim 13 , wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for the UE to receive contention resolution messages from the BS.

15. 10. The method of claim 9, wherein the bundled random access response message provides permission to transmit a connection request message, the permission indicating information about at least one of a transport block size (TBS), a bundling length, a sub-band hopping indicator, and a transmit power control (TPC).

16. 10. The method of claim 9, wherein timing of transmitting a connection request message is based at least in part on a bundling size of at least one of the bundled random access response messages or the connection request message.

17. 10. The method of claim 9, wherein at least one of a narrowband region or a bundling size of a contention resolution message from the BS is determined based at least in part on at least one of a narrowband region or a bundling size of the bundled random access response message.

18. applying a priority of the UE to determine a type of message to collect from the BS, wherein the type of message comprises one of a random access response message, a paging message, or a broadcast message carrying system information; 10. The method of claim 1, further comprising: monitoring for the type of message from the BS based at least in part on the priority of the UE.

19. 1. An apparatus for wireless communication, comprising: means for determining a number of subframes in which the device may transmit a bundled random access channel (RACH) message to a base station (BS); means for determining, within the plurality of subframes, at least one narrowband region for transmitting the bundled RACH message; means for determining a bundling size for the bundled RACH messages, the bundling size indicating a number of the plurality of subframes over which the bundled RACH messages are transmitted; and means for transmitting the bundled RACH message in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size.

20. 20. The apparatus of claim 19, wherein the plurality of subframes is determined based at least in part on a particular subframe available as a starting subframe for the bundled RACH message.

21. 20. The apparatus of claim 19, wherein the bundling size for the bundled RACH messages is determined based at least in part on broadcast signaling from the BS.

22. 20. The apparatus of claim 19, wherein the bundling size for the bundled RACH messages is determined based at least in part on a location of the at least one narrowband region or a starting subframe of the bundled RACH messages.

23. 20. The apparatus of claim 19, wherein the bundling size for the bundled RACH messages is determined based at least in part on an estimated coverage extension target.

24. 20. The apparatus of claim 19, wherein the bundling size for the bundled RACH message is determined based at least in part on the success or failure of the BS to successfully decode a previous bundled RACH message.

25. 25. The apparatus of claim 24, further comprising means for decoding a random access response message, wherein the success or failure is determined at least in part based on successfully decoding the random access response message from the BS for a previously transmitted bundled RACH message.

26. in response to the BS's failure to successfully decode the previous bundled RACH message. the bundling size for the bundled RACH message relative to a bundling size for the previous bundled RACH message; or 25. The apparatus of claim 24, further comprising: means for increasing at least one of the transmit powers for the bundled RACH messages relative to a transmit power for the previous bundled RACH message.

27. The apparatus of claim 19 , further comprising: means for receiving a bundled random access response message from the BS.

28. 28. The apparatus of claim 27, wherein at least one of a narrowband region or a bundling size of the control portion of the bundled random access response message is based at least in part on a determination of at least one property from the selected bundled RACH message.

29. 30. The apparatus of claim 27, wherein the at least one property comprises at least one of the at least one narrowband region or the bundling size of the bundled RACH message.

30. 30. The apparatus of claim 27, wherein timing of the bundled random access response messages is based at least in part on the bundling size of the bundled RACH messages.

31. 30. The apparatus of claim 27, 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 bundling size for the apparatus to transmit the connection request message.

32. 32. The apparatus of claim 31, further comprising means for receiving a contention resolution message, wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for which the apparatus receives the contention resolution message from the BS.

33. 28. The apparatus of claim 27, further comprising means for transmitting a connection request message, wherein the bundled random access response message provides permission to transmit the connection request message, the permission indicating information about at least one of a transport block size (TBS), a bundling length, a sub-band hopping indicator, and a transmit power control (TPC).

34. 30. The apparatus of claim 27, 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 bundling size of at least one of the bundled random access response messages or the connection request message.

35. 28. The apparatus of claim 27, further comprising means for receiving a contention resolution message from the BS, wherein at least one of a narrowband region or a bundling size of the contention resolution message from the BS is determined based at least in part on at least one of a narrowband region or a bundling size of the bundled random access response message.

36. means for applying a priority of the device to determine a type of message to collect from the BS, wherein the type of message comprises one of a random access response message, a paging message, or a broadcast message carrying system information; 20. The apparatus of claim 19, further comprising: means for monitoring for the type of messages from the BS based at least in part on the priority of the device.

37. 1. An apparatus for wireless communication, comprising: determining a number of subframes in which the device may transmit a bundled random access channel (RACH) message to a base station (BS); determining at least one narrowband region within the plurality of subframes for transmitting the bundled RACH message; determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted; At least one processor configured to: a transmitter configured to transmit the bundled RACH message in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size; and a memory coupled to the at least one processor.

38. 16. A computer-readable medium for wireless communication by a user equipment (UE), comprising: code for determining a number of subframes in which the UE may transmit a bundled random access channel (RACH) message to a base station (BS); code for determining at least one narrowband region within the plurality of subframes for transmitting the bundled RACH message; a code for determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted; and code for transmitting the bundled RACH message in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size.

39. A method for wireless communication by a base station (BS), comprising: determining a number of subframes in which a user equipment (UE) may transmit a bundled random access channel (RACH) message to the BS; determining at least one narrowband region within the plurality of subframes for receiving the bundled RACH message; determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted by the UE; receiving the bundled RACH message in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size.

40. 40. The method of claim 39, wherein the plurality of subframes is determined based at least in part on a particular subframe available as a starting subframe for the bundled RACH message.

41. 40. The method of claim 39, wherein the bundling size for the bundled RACH messages is determined based at least in part on broadcast signaling from the BS.

42. 40. The method of claim 39, wherein the bundling size for the bundled RACH messages is determined based at least in part on a location or a starting subframe of the at least one narrowband region of the bundled RACH messages.

43. 40. The method of claim 39, wherein the bundling size for the bundled RACH messages is determined based at least in part on an estimated coverage extension target.

44. 40. The method of claim 39, wherein the bundling size for the bundled RACH messages is determined based at least in part on the success or failure of the BS to successfully decode a previous bundled RACH message.

45. 45. The method of claim 44, wherein the success or failure is determined at least in part based on the UE successfully decoding a random access response message from the BS for a previous bundled RACH message.

46. 40. The method of claim 39, further comprising transmitting a bundled random access response message from the BS.

47. 47. The method of claim 46, wherein at least one of a narrowband region or a bundling size of the 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 message.

48. 48. The method of claim 47, wherein the at least one property from the bundled RACH message comprises at least one of the at least one narrowband region or the bundling size of the bundled RACH message.

49. 47. The method of claim 46, wherein the timing of the random access response message is based at least in part on the bundling size of the bundled RACH messages.

50. 47. The method of claim 46, wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for the UE to transmit a connection request message.

51. 51. The method of claim 50, wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for the UE to receive contention resolution messages from the BS.

52. 47. The method of claim 46, wherein the bundled random access response message provides permission to transmit a connection request message, the permission indicating information about at least one of a transport block size (TBS), a bundling length, a sub-band hopping indicator, and a transmit power control (TPC).

53. 47. The method of claim 46, wherein timing of receiving a connection request message is based at least in part on a bundling size of at least one of the bundled random access response messages or the connection request messages.

54. 47. The method of claim 46, wherein at least one of a narrowband region or a bundling size of a contention resolution message from the BS is determined based at least in part on at least one of a narrowband region or a bundling size of the bundled random access response message.

55. 1. An apparatus for wireless communication, comprising: means for determining a number of subframes in which a user equipment (UE) may transmit a bundled random access channel (RACH) message to the device; means for determining, within the plurality of subframes, at least one narrowband region for receiving the bundled RACH message; means for determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted by the UE; and means for receiving the bundled RACH message in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size.

56. 56. The apparatus of claim 55, wherein the plurality of subframes is determined based at least in part on a particular subframe available as a starting subframe for the bundled RACH message.

57. 56. The apparatus of claim 55, wherein the bundling size for the bundled RACH messages is determined based at least in part on broadcast signaling from the apparatus.

58. 56. The apparatus of claim 55, wherein the bundling size for the bundled RACH messages is determined based at least in part on a location of the at least one narrowband region or a starting subframe of the bundled RACH messages.

59. 56. The apparatus of claim 55, wherein the bundling size for the bundled RACH messages is determined based at least in part on an estimated coverage extension target.

60. 56. The apparatus of claim 55, wherein the bundling size for the bundled RACH message is determined based at least in part on the success or failure of the apparatus to successfully decode a previous bundled RACH message.

61. 61. The apparatus of claim 60, wherein the success or failure is determined based at least in part on the UE successfully decoding a random access response message from the apparatus for a previous bundled RACH message.

62. 56. The apparatus of claim 55, further comprising means for transmitting a bundled random access response message from the apparatus.

63. 63. The apparatus of claim 62, wherein at least one of a narrowband region or a bundling size of the control portion of the bundled random access response message is based at least in part on a determination of at least one property from the bundled RACH message.

64. 64. The apparatus of claim 63, wherein the at least one property from the bundled RACH message comprises at least one of the at least one narrowband region or the bundling size of the bundled RACH message.

65. 63. The apparatus of claim 62, wherein timing of the bundled random access response messages is based at least in part on the bundling size of the bundled RACH messages.

66. 63. The apparatus of claim 62, wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for the UE to transmit a connection request message.

67. 67. The apparatus of claim 66, wherein the bundled random access response message indicates at least one of a narrowband region or a bundling size for the UE to receive contention resolution messages from the apparatus.

68. 63. The apparatus of claim 62, wherein the bundled random access response message provides permission to transmit a connection request message, the permission indicating information about at least one of a transport block size (TBS), a bundling length, a subband hopping indicator, and a transmit power control (TPC).

69. 63. The apparatus of claim 62, 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 bundling size of at least one of the bundled random access response messages or the connection request message.

70. 63. The apparatus of claim 62, further comprising means for transmitting a contention resolution message, wherein at least one of a narrowband region or a bundling size of the contention resolution message from the apparatus is determined based at least in part on at least one of a narrowband region or a bundling size of the bundled random access response message.

71. 1. An apparatus for wireless communication, comprising: determining a number of subframes in which a user equipment (UE) may transmit a bundled random access channel (RACH) message to the device; determining at least one narrowband region within the plurality of subframes for receiving the bundled RACH message; determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted by the UE; At least one processor configured to: a receiver configured to receive the bundled RACH messages in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size; and a memory coupled to the at least one processor.

72. 1. A computer-readable medium for wireless communication by a base station (BS), the computer-readable medium comprising: code for determining a number of subframes in which a user equipment (UE) may transmit a bundled random access channel (RACH) message to the BS; code for determining, within the plurality of subframes, at least one narrowband region for receiving the bundled RACH message; a code for determining a bundling size for the bundled RACH message, the bundling size indicating a number of the plurality of subframes in which the bundled RACH message is transmitted by the UE; and code for receiving the bundled RACH messages in the at least one narrowband region of the plurality of subframes based at least in part on the determined bundling size.

73. selecting a random access channel (RACH) preamble from a set of RACH preambles; transmitting a physical RACH (PRACH) message comprising the RACH preamble; determining a random access response (RAR) resource for receiving a RAR message based at least in part on the RACH preamble; and and receiving the RAR message on the RAR resource.

74. identifying one or more control channel decoding candidates based at least in part on the RACH preamble; 74. The method of claim 73, further comprising blindly decoding the one or more control channel candidates.

75. 75. The method of claim 74, wherein identifying the one or more control channel decoding candidates comprises determining at least one of an aggregation level, an RAR message bundling size, or an RAR message packet size.

76. 76. The method of claim 75, wherein the aggregation level comprises an extended control channel element (ECCE).

77. 76. The method of claim 75, wherein the RAR message packet size is based at least in part on the RACH preamble.

78. 74. The method of claim 73, wherein the RACH preamble is selected based at least in part on a bundling size of the RAR message.

79. 74. The method of claim 73, wherein the RAR resource comprises at least one of a narrowband frequency region of a carrier bandwidth, a starting transmission time, a starting subframe, or an RAR message bundling size.

80. 80. The method of claim 79, wherein the RAR message bundling size is independent of the PRACH message bundling size.

81. receiving a Physical Random Access Channel (PRACH) message comprising a RACH preamble; and selecting a random access response (RAR) resource for transmitting a RAR message based at least in part on the RACH preamble.

82. 82. The method of claim 81, further comprising determining a bundling size for the RAR message based at least in part on the RACH preamble.

83. 1. An apparatus for wireless communication, comprising: means for selecting a random access channel (RACH) preamble from a set of RACH preambles; means for transmitting a physical RACH (PRACH) message comprising the RACH preamble; means for determining a random access response (RAR) resource for receiving a RAR message based at least in part on the RACH preamble; and means for receiving the RAR message on the RAR resource.

84. means for identifying one or more control channel decoding candidates based at least in part on the RACH preamble; and means for blind decoding the one or more control channel candidates.

85. 85. The apparatus of claim 84, wherein the means for identifying the one or more control channel decoding candidates comprises means for determining at least one of an aggregation level, an RAR message bundling size, or an RAR message packet size.

86. 86. The apparatus of claim 85, wherein the aggregation level comprises an extended control channel element (ECCE).

87. 86. The apparatus of claim 85, wherein the RAR message packet size is based at least in part on the RACH preamble.

88. 84. The apparatus of claim 83, wherein the RACH preamble is selected based at least in part on a bundling size of the RAR message.

89. 84. The apparatus of claim 83, wherein the RAR resource comprises at least one of a narrowband frequency region of a carrier bandwidth, a starting transmission time, a starting subframe, or an RAR message bundling size.

90. 90. The apparatus of claim 89, wherein the RAR message bundling size is independent of a PRACH message bundling size.

91. 1. An apparatus for wireless communication, comprising: means for receiving a Physical Random Access Channel (PRACH) message comprising a RACH preamble; and means for selecting a random access response (RAR) resource for transmitting a RAR message based at least in part on the RACH preamble.

92. 92. The apparatus of claim 91, further comprising: means for determining a bundling size for the RAR message based at least in part on the RACH preamble.

93. 1. An apparatus for wireless communication, comprising: selecting a random access channel (RACH) preamble from a set of RACH preambles; transmitting, via a transmitter, a physical RACH (PRACH) message comprising the RACH preamble; determining a random access response (RAR) resource for receiving a RAR message based at least in part on the RACH preamble; and receiving, via a receiver, the RAR message on the RAR resource; At least one processor configured to: and a memory coupled to the at least one processor.

94. The at least one processor: identifying one or more control channel decoding candidates based at least in part on the RACH preamble; 94. The apparatus of claim 93, further configured to: blindly decode the one or more control channel candidates.

95. 95. The apparatus of claim 94, wherein the at least one processor is configured to determine at least one of an aggregation level, an RAR message bundling size, or an RAR message packet size.

96. 96. The apparatus of claim 95, wherein the aggregation level comprises an extended control channel element (ECCE).

97. 96. The apparatus of claim 95, wherein the RAR message packet size is based at least in part on the RACH preamble.

98. 94. The apparatus of claim 93, wherein the RACH preamble is selected based at least in part on a bundling size of the RAR message.

99. 94. The apparatus of claim 93, wherein the RAR resource comprises at least one of a narrowband frequency region of a carrier bandwidth, a starting transmission time, a starting subframe, or an RAR message bundling size.

100. 100. The apparatus of claim 99, wherein the RAR message bundling size is independent of a PRACH message bundling size.

101. 1. An apparatus for wireless communication, comprising: a receiver configured to receive a Physical Random Access Channel (PRACH) message comprising a RACH preamble; at least one processor configured to select a random access response (RAR) resource for transmitting a RAR message based at least in part on the RACH preamble; and a memory coupled to the at least one processor.

102. 102. The apparatus of claim 101, wherein the at least one processor is further configured to determine a bundling size for the RAR message based at least in part on the RACH preamble.

103. code for selecting a random access channel (RACH) preamble from a set of RACH preambles; code for transmitting a physical RACH (PRACH) message comprising the RACH preamble; code for determining a random access response (RAR) resource for receiving a RAR message based at least in part on the RACH preamble; and code for receiving the RAR message on the RAR resource.

104. code for identifying one or more control channel decode candidates based at least in part on the RACH preamble; and code for blind decoding the one or more control channel candidates.

105. 105. The non-transitory computer-readable medium of claim 104, wherein the code for identifying the one or more control channel decoding candidates comprises code for determining at least one of an aggregation level, an RAR message bundling size, or an RAR message packet size.

106. 106. The non-transitory computer-readable medium of claim 105, wherein the aggregation level comprises an extended control channel element (ECCE).

107. 106. The non-transitory computer-readable medium of claim 105, wherein the RAR message packet size is based at least in part on the RACH preamble.

108. 104. The non-transitory computer-readable medium of claim 103, wherein the RACH preamble is selected based at least in part on a bundling size of the RAR message.

109. 104. The non-transitory computer-readable medium of claim 103, wherein the RAR resource comprises at least one of a narrowband frequency region of a carrier bandwidth, a starting transmission time, a starting subframe, or a RAR message bundling size.

110. 110. The non-transitory computer-readable medium of claim 109, wherein the RAR message bundling size is independent of a PRACH message bundling size.

111. code for receiving a Physical Random Access Channel (PRACH) message comprising a RACH preamble; and code for selecting a random access response (RAR) resource for transmitting a RAR message based at least in part on the RACH preamble.

112. 112. The non-transitory computer-readable medium of claim 111, further comprising code for determining a bundling size for the RAR message based at least in part on the RACH preamble.

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