RU2779259C2 - Signaling level of coverage improvement and effective packaging of mtn system information - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: device for transmission of system information in a wireless communication system supporting coverage improvement contains a control circuit, which, during operation, generates system information including information elements common for different levels of coverage improvement, and one or more information elements characteristic for different levels of coverage improvement, and a transmitter, which, during operation, transmits generated system information with set periodicity.

EFFECT: increase in the efficiency of transmission and reception of system information in a wireless network supporting coverage improvement.

14 cl, 10 dwg, 2 tbl

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001] The present disclosure relates to the transmission and reception of system information in a wireless communication system.

BACKGROUND OF THE INVENTION

[0002] Third generation (3G) mobile communication systems based on WCDMA radio access technology are being deployed on a large scale throughout the world. The first step in improving or developing this technology involves the introduction of High Speed Downlink Packet Access (HSDPA) and enhanced uplink, also referred to as High Speed Uplink Packet Access (HSUPA), providing a radio access technology that is highly competitive. .

[0003] To be prepared for further growth in user demand and to be competitive with new radio access technologies, 3GPP has introduced a new mobile communication system called the Long Term Evolution (LTE) Project. LTE is designed to meet the carrier needs for high-speed data and multimedia transport as well as high-capacity voice support for the next decade. The ability to provide high bit rates is a key feature for LTE.

[0004] The Long Term Evolution (LTE) Project Working Element (WI) specification, called Enhanced UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial Radio Access Network (UTRAN), has been completed as Release 8 (Rel. 8 LTE). The LTE system introduces efficient packet-based radio access and radio access networks that provide full IP-based functionality with low latency and low cost. In LTE, a scalable set of transmission bandwidths such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz are defined to achieve flexible system deployment using a given spectrum. In the downlink, radio access based on Orthogonal Frequency Division Multiplexing (OFDM) has been adopted due to its intrinsic multipath interference (MPI) robustness due to low symbol rate, use of cyclic prefix (CP), and its ability to various layouts. bandwidth for transmission. In the uplink, radio access based on Single Carrier Frequency Division Multiple Access (SC-FDMA) has been adopted since providing global coverage has been prioritized over improvement in peak data rate given the limited transmit power of the user equipment (UE). Many key packet radio access technologies are used, including multiple input multiple output (MIMO) channel transmission technologies, and a highly efficient control signaling structure is achieved in LTE Release 8/9.

[0005] The general architecture is shown in FIG. 1 and a more detailed representation of the E-UTRAN architecture is given in FIG. 2. The E-UTRAN consists of an eNodeB providing E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol endpoints towards the user equipment (UE). The eNodeB (eNB) contains the Physical (PHY), Media Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers that include user plane header compression and encryption functionality. It also offers Radio Resource Control (RRC) functionality corresponding to the control plane. It performs many functions, including radio resource management, access control, scheduling, enforcement of uplink consistent quality of service (QoS), cell information broadcast, user and control plane data encryption/decryption, and downlink user plane packet header compression/decompression. link/uplink. The eNodeBs are mutually connected to each other via the X2 interface.

[0006] The eNodeBs are also connected via an S1 interface to an EPC (Enhanced Packet Network Core), more specifically, to an MME (Mobility Management Entity) via an S1-MME, and to a Serving Gateway (SGW) via an S1-U. The S1 interface maintains a many-to-many relationship between MMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user data packets, while also acting as a mobility anchor for the user plane during handoffs between eNodeBs and as a mobility anchor between LTE and other 3GPP technologies (terminating the S4 interface and relaying traffic between 2G/ 3G and PDN GW). For idle state user equipments, the SGW terminates the downlink data path and starts paging when the downlink data arrives for the user equipment. It manages and stores user equipment contexts such as IP bearer service parameters, network internal routing information. It also replicates user traffic in case of legitimate interception.

[0007] The MME is a key control node for the LTE access network. It is responsible for idle mode user equipment tracking and paging procedure, including retransmissions. It is used in the bearer activation/deactivation process and is also responsible for selecting the SGW for the user equipment at initial attachment and during intra-LTE handover including Core Network (CN) node re-discovery. It is responsible for user authentication (through interaction with the HSS). Non-Access Layer (NAS) signaling terminates at the MME and is also responsible for generating and assigning temporary identities for user equipments. It verifies the user equipment's authorization to be based in the service provider's Public Land Mobile Network (PLMN) and enforces user equipment roaming restrictions. The MME is the network endpoint for encryption/integrity protection for NAS signaling and handles security key management. Lawful signaling interception is also supported by the MME entity. The MME also provides a control plane function for mobility between LTE and 2G/3G access networks via the S3 interface ending in the MME of the SGSN. The MME also terminates the S6a interface towards the home HSS for user equipment roaming.

[0008] FIG. 3 shows a radio frame structure for LTE FDD. The downlink component carrier of the 3GPP LTE system (Release 8 and beyond) is subdivided in the time-frequency domain into radio frames, which are further subdivided into so-called subframes. In 3GPP LTE (Release 8 and beyond), each subframe is divided into two downlink slots, one of which is shown in FIG. 4. The first downlink slot contains a control channel region (PDCCH region) within the first OFDM symbols. Each subframe consists of a given number of OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE Release 8 and beyond), with each OFDM symbol covering the entire bandwidth of the component carrier. The OFDM symbols thus each consist of a number of modulation symbols transmitted on the respective N ^DL _RB *N ^RB _SC subcarriers. Assuming a multi-carrier communication system, eg using OFDM, such as used in 3GPP Long Term Evolution (LTE), the smallest resource unit that can be assigned by a scheduler is one "resource block". A physical resource block (PRB) is defined as N ^DL _symb consecutive OFDM symbols in the time domain (eg, 7 OFDM symbols) and N ^RB _SC consecutive subcarriers in the frequency domain, as illustrated in FIG. 4 (eg, 12 subcarriers for a component carrier). In 3GPP LTE (Release 8), a physical resource block thus consists of N ^DL _symb *N ^RB _SC resource elements corresponding to one slot in the time domain and 180 kHz in the frequency domain (for further details regarding the downlink resource grid , see for example 3GPP TS 36.211, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)" (NPL 1), section 6.2, available at http://www.3gpp.org and included here by reference).

[0009] One subframe consists of two slots, so there are 14 OFDM symbols per subframe when the so-called "normal" CP (cyclic prefix) is used, and 12 OFDM symbols per subframe when the so-called "extended" CP is used. For terminology, in the following, time-frequency resources equivalent to the same N ^RB _SC consecutive subcarriers spanning a complete subframe are referred to as "resource block pair", or equivalently "RB pair" or "PRB pair".

[0010] The feature "component carrier" indicates a combination of multiple resource blocks in the frequency domain. In future releases of LTE, the feature "component carrier" is no longer used; instead, the terminology is changed to "cell", which indicates a combination of downlink and optionally uplink resources. The relationship between the carrier frequency of the downlink resources and the carrier frequency of the uplink resources is indicated in the system information carried in the downlink resources.

[0011] Similar assumptions for the component carrier structure apply to later releases as well.

[0012] The downlink control information appears in several formats that differ in overall size and also in the information contained in its fields. The various DCT formats currently defined for LTE are as follows and are described in detail in 3GPP TS 36.212, "Multiplexing and channel coding"(NPL 2), section 5.3.3.1 (available at http://www.3gpp.org and included here by reference). For more information regarding DCT formats and the specific information that is carried in DCT, please see the technical standard or LTE - The UMTS Long Term Evolution - From Theory to Practice, edited by Stefanie Sesia, Issam Toufik, Matthew Baker, chapter 9.3 (NPL 3 ), included here by reference.

[0013] In order for the UE to identify whether it received the PDCCH transmission correctly, error detection is provided by a 16-bit CRC added to each PDCCH (ie, DCT). Additionally, it is necessary for the UE to be able to identify which PDCCH channels (channel) are intended for it. This can in theory be achieved by adding an identifier to the PDCCH payload; however, it is more efficient to scramble the CRC with the "UE Identity Information", which saves overhead. The CRC may be computed and scrambled as specified in detail by 3GPP in TS 36.212, section 5.3.3.2 "CRC attachment", which is incorporated herein by reference. This section describes how error detection in DCT transmissions is provided by cyclic redundancy check (CRC). A summary is given below.

The full payload is used to calculate the CRC parity bits. The parity bits are calculated and appended. In the case where the UE transmit antenna selection is not configured or applicable, after attaching, the CRC parity bits are scrambled with the corresponding RNTI.

[0014] The scrambling may further depend on the choice of the UE's transmit antenna, as seen in TS 36.212. In the case where the UE transmit antenna selection is configured and applicable, after attaching, the CRC parity bits are scrambled with the antenna selection mask and the corresponding RNTI. Since in both cases the RNTI is used in the scrambling operation, for simplicity and without loss of generality, the following description of the embodiments simply refers to a CRC that is scrambled (and descrambled as applicable) with the RNTI, which should therefore be understood regardless of, for example, an additional element in the scrambling processing, such as an antenna selection mask.

[0015] Accordingly, the UE descrambles the CRC by applying the "UE Identity Information", and if no CRC error is detected, the UE determines that the PDCCH is transmitting its control information intended for itself. The terminology "masking" and "de-masking" is also used for the above-described processing of CRC scrambling with identification information.

[0016] The "UE Identity Information" mentioned above, with which the CRC of the DCI may be scrambled, may also be an SI-RNTI (Radio Network Temporary Identifier for System Information), which is not a "UE Identity Information" per se, but rather an identifier, associated with the type of information that is indicated and transmitted, in this case system information. The SI-RNTI is usually fixed in the specification and thus known a priori for all UEs.

[0017] There are different types of RNTIs that are used for different purposes. The following tables, taken from 3GPP 36.321 Chapter 7.1 (NPL 4), should give an overview of the various 16-bit RNTIs and their uses.

[0018] [Table 1]

Value (hexadecimal) RNTI 0000 not applicable 0001-003C RA-RNTI, C-RNTI, Semi-Permanent Scheduling C-RNTI, Temporary C-RNTI, TPC-PUCCH-RNTI and TPC-PUSCH-RNTI (see note) 003D-FFF3 C-RNTI, Semi-Permanent Scheduling C-RNTI, Interim C-RNTI, TPC-PUCCH-RNTI and TPC-PUSCH-RNTI FFF4-FFFC Reserved for future use FFFD M-RNTI FFFE P-RNTI FFFF SI-RNTI

[0019] Physical Downlink Control Channel (PDCCH) and Physical Downlink Shared Channel (PDSCH)

[0020] The Physical Downlink Control Channel (PDCCH) transmits, for example, scheduling grants for assigning resources for downlink or uplink data transmission. A plurality of PDCCHs may be transmitted in a subframe.

[0021] The PDCCH for user equipments is transmitted in the first N ^PDCCH _symb OFDM symbols (typically any 1, 2 or 3 OFDM symbols as specified by PCFICH, exceptionally any 2, 3, or 4 OFDM symbols as specified via PCFICH) within a subframe, extending across the entire system bandwidth; the system bandwidth is typically equivalent to cell or component carrier coverage. The region occupied by the first N ^PDCCH _symb OFDM symbols in the time domain and the N ^DL _RB *N ^RB _SC subcarriers in the frequency domain is also referred to as the PDCCH region or the control channel region. The remaining N ^PDSCH _symb =2*N ^DL _symb -N ^PDCCH _symb OFDM symbols in the time domain per N ^DL _RB *N ^RB _SC subcarriers in the frequency domain is referred to as the PDSCH region or the shared channel region (see below).

[0022] To provide a downlink (ie, resource assignment) on a physical downlink shared channel (PDSCH), the PDCCH assigns a PDSCH resource to (user) data within the same subframe. The PDCCH control channel area within a subframe consists of a set of CCEs, where the total number of CCEs in the subframe control area is distributed over the time and frequency control resource. A plurality of CCEs may be combined to effectively reduce the coding rate of the control channel. The CCEs are combined in a predetermined manner using a tree structure to achieve different coding rates.

[0023] At the transport channel layer, information transmitted on the PDCCH is also referred to as L1/L2 control signaling (see above for details on L1/L2 control signaling).

[0024] A general method for detecting and correcting errors in packet transmission systems over unreliable channels is called hybrid automatic repeat request (HARQ). Hybrid ARQ is a combination of Forward Error Correction (FEC) and ARQ.

[0025] If an FEC encoded packet is transmitted and the receiver fails to correctly decode the packet (errors are usually checked by CRC (cyclic redundancy check)), the receiver requests retransmission of the packet. In general (and throughout this document) the transmission of additional information is called "retransmission (of a packet)", although this retransmission does not necessarily mean the transmission of the same encoded information, but can also mean the transmission of any information belonging to the packet (e.g., additional information redundancy).

[0026] Depending on the information (in general, code bits/symbols) whose transmission is being assembled, and depending on how the receiver processes the information, the following hybrid ARQ schemes are defined:

[0027] In Type I HARQ schemes, the encoded packet information is discarded and a retransmission is requested if the receiver fails to correctly decode the packet. This has the consequence that all transmissions are decoded separately. In general, retransmissions contain identical information (code bits/symbols) with the initial transmission.

[0028] In Type II HARQ schemes, a retransmission is requested if the receiver fails to correctly decode the packet, where the receiver stores the information of the (erroneously received) encoded packet as soft information (soft bits/symbols). This has the consequence that a soft buffer is required at the receiver. Retransmissions may be composed of identical, partially identical or non-identical information (code bits/symbols) according to the same packet as earlier transmissions. Upon receiving the retransmission, the receiver combines the stored information from the soft buffer and the currently received information, and attempts to decode the packet based on the combined information. (The receiver may also attempt to decode the transmission individually, however, in general, performance is increased by combining transmissions.) Transmission combining indicates so-called soft combining, where a plurality of received code bits/symbols are combined with a likelihood and single received code bits/symbols are combined in a coded fashion. . Common methods for soft combining are maximum ratio combining (MRC) of received modulation symbols and log-likelihood ratio (LLR) combining (LLR combining only works for code bits).

[0029] Type II schemes are more complex than type I schemes because the probability for correctly receiving a packet increases with each received retransmission. This increase comes at the expense of the required hybrid ARQ soft buffer at the receiver. This scheme may be used to perform dynamic link adaptation by controlling the amount of information to be retransmitted. For example, if the receiver detects that the decoding was "almost" successful, it may only request a small portion of the information for the next retransmission (fewer code bits/symbols than in the previous transmission) for transmission. In this case, it may happen that it is theoretically not even possible to correctly decode the packet by taking into account only this retransmission by itself (non-self-decodable retransmissions).

[0030] Type III HARQ schemes can be considered as a subset of type II schemes: in addition to the requirements of a type II scheme, each transmission in a type III scheme must be self-decodable.

[0031] Synchronous HARQ means that retransmissions of HARQ blocks occur at predetermined periodic intervals. Therefore, no explicit signaling is required to indicate to the receiver the retransmission scheduling.

[0032] Asynchronous HARQ offers flexibility in scheduling retransmissions based on air interface conditions. In this case, some identification of the HARQ process must be signaled to allow for a correct combination and protocol operation. In 3GPP LTE systems, eight-process HARQ operations are used. The operation of the HARQ protocol for downlink data transmission will be similar or even identical to HSDPA.

[0033] In the uplink HARQ protocol operation, there are two different choices regarding how to schedule retransmission. Retransmissions are either "scheduled" by NACK (also referred to as synchronous non-adaptive retransmission) or explicitly scheduled by the network by PDCCH transmission (also referred to as synchronous adaptive retransmissions). In the case of synchronous non-adaptive retransmission, the retransmission will use the same parameters as the previous uplink transmission, i.e., the retransmission will be signaled on the same physical channel resources, thus using the same modulation scheme/transport format.

[0034] Since synchronous adaptive retransmissions are explicitly scheduled by the PDCCH, the eNodeB is able to change some parameters for retransmission. The retransmission may, for example, be scheduled on a different frequency resource to avoid uplink fragmentation, or the eNodeB may change the modulation scheme or alternatively indicate to the user equipment which redundancy version to use for retransmission. Note that HARQ (ACK/NACK) feedback and PDCCH signaling occur at the same time. Therefore, the user equipment only needs to check once if synchronous non-adaptive retransmission is triggered (ie, only NACK is received) or if the eNode B is requesting synchronous adaptive retransmission (ie, PDCCH is signaled).

[0035] Receiving system information (SI) is an operation to be performed by the UE based on the scanned RF signal and the detected synchronization signal. In particular, upon detection of synchronization signals, the UE is capable of identifying the cell and synchronizing with the cell's downlink transmissions. Accordingly, the UE may receive the broadcast channel, BCH, cells, and hence the corresponding system information. Based on this, the UE can detect whether or not the cell is suitable for selection and/or reselection, that is, whether the cell is a candidate cell.

[0036] System information is information that is broadcast in a broadcast manner to all UEs in a cell. It includes information necessary for cell selection, and some parts of it must be read on any cell selection/reselection after the UE has synchronized with the cell.

[0037] System information is structured by system information blocks (SIBs), each of which includes a set of parameters. In particular, system information is carried in the main information block, MIB, and a number of system information blocks. The MIB includes a limited number of the most significant and most frequently transmitted parameters that are needed to obtain other information from the cell, such as downlink system bandwidth, an indicator of resources assigned to downlink HARQ handshake signaling, and a system frame number ( SFN). The remaining SIBs are numbered; there are SIBs 1 to 13 defined in Release 8.

[0038] SIB1 contains parameters necessary to determine whether a cell is suitable for cell selection, as well as time domain scheduling information of other SIBs. SIB2 includes common and shared channel information. SIBs 3 to 8 include parameters used to control intra-frequency, inter-frequency and inter-radio access technologies (RAT) cell reselection. SIB9 is used to signal the name of the home eNodeB, while SIBs 10 to 12 include Earthquake and Tsunami Warning Service (ETWS) notifications and Commercial Mobile Alarm System (CMAS) alert messages. Finally, SIB 13 includes MBMS related control information.

[0039] System information is transmitted via the RRC protocol in three types of messages: MIB message, SIB1 message, and SI message. The MIB messages are transmitted on the Physical Broadcast Channel (PBCH), while the remaining SIB1 and SI messages are physically multiplexed with the unidirectional data transmitted on the Physical Downlink Shared Channel (PDSCH).

[0040] MIB is transmitted with fixed cycles. SIB1 is also transmitted with fixed cycles. In order to improve the robustness of the transmission of system information, the system information is repeated. The repetitions have different versions of redundancy and thus they are not repetitions of the bits actually transmitted, but rather repetitions of the transmitted data but coded differently. For example, a MIB is transmitted every frame in the first subframe (subframe #0), with a new MIB (MIB with content possibly different from previous MIBs) being transmitted every four frames and the remaining three frames carrying its repetition. Similarly, repetition coding is applied to the transmission of the SIB1 block. A new SIB1 is transmitted every 8 frames. Each SIB1 has three additional repetitions. All other SIBs are transmitted at cycles determined by the SIB scheduling information elements in SIB1. In particular, the mapping of SIBs to an SI message is highly configurable by the schedulingInfoList included in SIB1, with the restriction that each SIB is only contained in a single SI message, and at most once in that message. Only SIBs having the same scheduling requirement (periodicity) may be mapped to the same SI message; SIB2 is always mapped to the SI message that matches the first entry in the list of SI messages in the schedulingInfoList. There may be multiple SI messages transmitted at the same frequency.

[0041] That is, the terminal determines the SI window based on the signaling information, and starts receiving (blind decoding) the downlink shared channel using the SI-RNTI (an identifier indicating that signaling information is being transmitted) from the beginning of the SI window, and continues for each subframe until the end of the SI window or until an SI message is received, excluding subframe #5 in radio frames for which SFN mod 2=0, any MBSFN subframes, and any uplink subframes in TDD. If the SI message has not been received by the end of the SI window, the reception is repeated at the next occurrence of the SI window for the corresponding SI message.

[0042] In other words, during blind decoding, the UE attempts to decode the PDCCH in each subframe of the SI window with the SI-RNTI, but only some of these subframes actually carry the PDCCH (CRC) encoded using the SI-RNTI (corresponding to the PDSCH containing the specific SI).

[0043] For more details regarding the definition of system information, see, for example, 3GPP, TS 36.331, V12.5.0, "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification (Release 12)" (NPL 5), sections 6.2.2.7 and 6.3.1, available at http://www.3gpp.org and incorporated here by reference.

[0044] As LTE deployments evolve, operators are trying to reduce the cost of full network maintenance by minimizing the number of RAT technologies. In this respect, Machine Type Communications (MTC) devices are a market that is likely to continue to expand in the future.

[0045] Many MTC devices target low-end (low cost, low data rate) applications that can be handled adequately by GSM/GPRS. Due to the low cost of these devices and good GSM/GPRS coverage, there is very little motivation for MTC device vendors to use modules that support the LTE air interface.

[0046] As more and more MTC devices are deployed in the art, this naturally increases the utilization of GSM/GPRS networks. This will be costly for operators, not only in terms of supporting multiple RAT technologies, but will also prevent operators from getting the most out of their spectrum (given sub-optimal GSM/GPRS spectral efficiency). As users and traffic become denser, the use of more spectrally efficient technologies such as Long Term Evolution (LTE) enables operators to use their spectrum in a much more efficient way.

[0047] Given a likely large number of MTC devices, the total resource that they will need to provide services may be correspondingly significant, and allocated inefficiently (for more details on targets for MTC, see e.g. 3GPP, RP-150492 Ericsson: "Revised WI: Further LTE Physical Layer Enhancements for MTC" (NPL 6), section 4, available at http://www.3gpp.org and incorporated here by reference).

[0048] Cost reduction approaches for LTE currently consider product volume as a primary reason. The effect of volume can be seen in two possible ways, depending on how the low cost MTC develops. First, if low cost MTC can be very similar to underlying LTE and be included in LTE chipsets, MTC has the LTE volume advantage. Second, low-cost MTC based on LTE can have a significantly lower cost than underlying LTE. Although it does not appear to have the volume advantage of LTE, the volume of MTC devices may be even larger due to the potentially larger number of supported MTC applications and scenarios.

[0049] In this regard, the following approaches to reduce the cost of LTE, i.e., defining a low cost MTC, are discussed and found to have a significant impact on the cost of a UE (for more details regarding low cost MTC devices, see e.g. 3GPP , R1-112912, Huawei, HiSilicon, CMCC: "Overview on low-cost MTC UEs based on LTE" (NPL 7), section 4, available at http://www.3gpp.org and incorporated here by reference):

[0050] - Reduction in Supported Bandwidth for Low Cost LTE: The low cost of 1.4 MHz downlink bandwidth (6 RB) can cover most MTC application scenarios. However, 3 MHz (15 RB) or 5 MHz (25 RB) may be considered provided that the complexity does not increase greatly. Given that the uplink may have a larger requirement for MTC services, the possibility of reduced transmit power, and low baseband complexity (relative to downlink reception), any reduction in the minimum bandwidth for transmission to the UE must be carefully justified.

- Modified PDCCH-related design for low cost LTE to simplify PDCCH blind decoding and provide efficient channel access for a large number of MTC devices. Reduction in the maximum bandwidth (eg 1.4 MHz) naturally reduces the blind decoding of the PDCCH.

- Protocol simplification, including HARQ accounting, MAC protocol, RLC and RRC. Reduce signaling between low duty cycle MTC devices and the base station.

- Downshift selection of transmission modes to support coverage complexity and balance.

[0051] Additional considerations for low cost MTC devices relate to improved indoor coverage. A number of applications require indoor deployment of machine-type communication devices, MTCs, for example, in the basement of an apartment, or on indoor equipment that may be close to the ground floor, etc. These UEs will experience significantly higher air interface penetration loss than normal LTE devices. This effectively means that indoor coverage must be easily accessible and reliable: that is, it must provide a significant improvement over existing coverage.

[0052] Additionally, regarding the power consumption of low cost MTC devices, it should be noted that many applications require devices to have up to ten years of battery life. In this regard, currently available power-saving modes appear to be insufficient to achieve the intended battery life. In this regard, it is expected that additional methods should be proposed to significantly cut the power consumption of MTC devices, for example, by optimizing the signaling exchanges in the system to realize a battery life of up to ten years.

[0053] To improve indoor coverage (for low cost MTC devices), recent developments have focused on enhanced coverage mode, EC, which is applicable to UEs such as those operating in delay tolerant MTC applications. Another feature is "coverage extension". The corresponding work item in 3GPP Release 12 "Low cost & enhanced coverage MTC UE for LTE" concluded that additional complexity reduction of LTE devices for MTC can be achieved if additional complexity reduction techniques are supported, as seen in Technical Report TR 36.888, v 12.0 .0, "Machine-Type Communications (MTC) User Equipments (UEs)" (NPL 8), available at www.3gpp.org and incorporated here by reference. Technical report TR 36.888 concludes that the 15-20 dB coverage improvement goal for both FDD and TDD over the normal LTE service area can be achieved to support use cases where MTC devices are deployed in challenging locations, such as deep inside buildings, and to compensation for gain loss caused by complexity reduction techniques. MTC coverage enhancements are now expected to be introduced in 3GPP Release 13.

[0054] In general, MTC devices can be low complexity (LC) MTC devices (which basically forces the device to accept TBS of 1000 bits or less as a result of buffer size limitations and other implementation limitations), or enhanced coverage (EC) devices, which are assumed that support a large number of repetitions.

[0055] In other words, LC devices are low complexity devices that are supposed to be inexpensive devices with limited buffer sizes/simple implementation, etc., while EC devices are enhanced coverage devices that need to work in problematic situations like, for example, in a basement or largely far from the center of the honeycomb.

[0056] The overall goal is to define a new UE for MTC operation in LTE that allows for improved coverage and low power consumption. Some of the additional goals are given below:

[0057] - Reduced UE bandwidth of 1.4 MHz in downlink and uplink.

- Reduced bandwidth UEs must be able to operate within any system bandwidth.

- Frequency multiplexing of reduced bandwidth UEs and non-MTC UEs should be supported.

- The UE should only support 1.4 MHz RF bandwidth in the downlink and uplink.

- The allowed retrain time supported by the specification (eg ~0 ms, 1 ms) should be defined by RAN4.

- Reduced maximum transmit power.

- The maximum transmit power of the new power class of the UE must be determined by RAN4 and must support the integrated PA implementation.

- Reduced support for downlink transmission modes.

[0058] The following additional UE processing relaxations may also be considered within this work item:

- Reduced maximum transport block size for unidirectional and/or broadcast signaling.

- Reduced support for receiving multiple transmissions at the same time.

- Relaxed EVM transmission and/or reception requirement including limited modulation scheme. Reduced physical control channel processing (eg, reduced number of blind decoding attempts).

- Reduced physical data link processing (eg, relaxed downlink HARQ timeline or reduced number of HARQ processes).

- Reduced support for CQI/CSI report modes.

- A relative improvement in LTE coverage - corresponding to 15 dB for FDD - for the UE category/type defined above and other UEs operating in delay-tolerant MTC applications over their respective normal coverage should be possible. At least some of the following methods, which should be applicable for both FDD and TDD, may be considered to achieve this:

[0059] - Methods for Associating Subframes with HARQ for Physical Data Channels (eg, PDSCH, PUSCH)

- Eliminate the use of control channels (eg PCFICH, PDCCH)

- Repetition methods for control channels (eg PBCH, PRACH, (E)PDCCH)

- Ways to either eliminate or recur (e.g. PBCH, PHICH, PUCCH)

- Increasing uplink PSD with less granularity than 1 PRB

- Resource assignment using EPDCCH with scheduling and repetition between subframes (operation without EPDCCH can also be considered)

- New physical channel formats with repetition for SIB/RAR/paging

- New SIB for UEs with reduced bandwidth and/or improved coverage

- Techniques for increased reference symbol density and frequency hopping

- Relaxed "missed detection probability" for PRACH and initial system data acquisition time for UE for PSS/SSS/PBCH/SIBs can be considered long as long as the impact on UE power consumption can be kept at a reasonable level.

- Extension: Extension indicates resource information extension including time-frequency domain resources, or even extension using scrambling (or channelization) codes.

[0060] There may also be other methods than those listed above.

The amount of coverage improvement should be configurable per cell and/or per UE and/or per channel and/or channel group, so that there are different levels of coverage improvements. Different levels of coverage enhancement may mean different levels of CE methods that are applied to support the transmission and reception of a CE device. Relevant UE measurements and reports to support this functionality must be defined.

[0061] For more details, see, for example, Ericsson's 3GPP RP-141865 "Revised WI: Further LTE Physical Layer Enhancements for MTC" (NPL 9), available at http://www.3gpp.org and incorporated herein at link.

[0062] It should be noted that 15/20 dB coverage improvements for UEs in enhanced coverage mode relative to their nominal coverage means that UEs must be able to receive extremely low signal strengths. This applies not only to the initial scan operation, cell search and cell selection operation, but also to the subsequent communication scheme to be performed by the UE. As described above, there will be different CE levels depending on network support and UE functionality, eg 5/10/15 dB coverage extension.

[0063] Early attempts to define an enhanced coverage mode have focused on modifications to broadcasts. In this regard, discussions focused on retransmissions as being the main way to improve coverage. Repetitions can be applied to each channel to improve coverage.

[0064] An exemplary implementation of these retransmissions dictates that the same data be transmitted in multiple subframes. Still, it should be directly visible that these retransmissions will use more resources (time-frequency) than what is required for normal coverage UEs. RANI has indicated that the transport block size used for transmission to MTC devices will be less than 1000 bits.

[0065] Considering the above requirements, new information message scheduling will be needed to minimize system overhead as well as not to affect the system of previous releases and legacy UEs served by it.

LIST OF REFERENCES

NON-PAtent LITERATURE

[0066] NPL 1: 3GPP TS 36.211, "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8), version 8.9.0

NPL 2: 3GPP TS 36.212, "Multiplexing and channel coding", version 12.4.0

NPL 3: The UMTS Long Term Evolution - From Theory to Practice, edited by Stefanie Sesia, Issam Toufik, Matthew Baker, chapter 9.3

NPL 4: 3GPP 36.321, "Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocol specification", version 12.5.0

NPL 5: 3GPP, TS 36.331, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification (Release 12), version 12.5.0

NPL 6: 3GPP, RP-150492 Ericsson: "Revised WI: Further LTE Physical Layer Enhancements for MTC

NPL 7: 3GPP, R1-112912, Huawei, HiSilicon, CMCC: "Overview on low-cost MTC UEs based on LTE"

NPL 8: TR 36.888, "Machine-Type Communications (MTC) User Equipments (UEs)", version 12.0.0

NPL 9: 3GPP RP-141865 "Revised WI: Further LTE Physical Layer Enhancements for MTC"

SUMMARY OF THE INVENTION

[0067] One non-limiting and illustrative embodiment provides devices and methods for efficiently transmitting and receiving system information in a wireless network.

[0068] In one general aspect, the methods disclosed herein provide an apparatus for receiving system information in a wireless communication system supporting coverage enhancement, comprising: a receiving unit for receiving system information; a control unit for controlling the receiving unit for receiving system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system; and for receiving system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0069] In another general aspect, the methods disclosed herein provide an apparatus for transmitting system information in a wireless communication system supporting coverage improvement, comprising: a transmission unit for transmitting system information; a control unit for controlling the transmission unit for transmitting system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system; and for transmitting system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0070] In another general aspect, the methods disclosed herein provide a method for receiving system information in a wireless communication system supporting coverage enhancement, comprising the steps of: receiving system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the system wireless communication; and receiving system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0071] In one general aspect, the methods disclosed herein provide a method for transmitting system information in a wireless communication system supporting coverage enhancement, comprising: transmitting system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless system. communications; and transmitting system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0072] It should be noted that general or specific embodiments may be implemented as a system, method, integrated circuit, computer program, storage medium, or any selective combination of the foregoing.

[0073] Additional benefits and advantages of the disclosed embodiments will become apparent from the description and drawings. Benefits and/or advantages may be individually obtained through various embodiments and features from the description and drawings, which do not all need to be provided in order to obtain one or more of such benefits and/or advantages.

[0074] The above and other objects and features of the present disclosure will become clearer from the following description and preferred embodiments given in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] [Fig. 1] FIG. 1 is a block diagram illustrating the current 3GPP architecture for machine-type communication.

[Fig. 2] FIG. 2 is a block diagram illustrating an exemplary radio access network architecture in 3GPP LTE.

[Fig. 3] FIG. 3 is a schematic diagram showing a general frame structure in 3GPP LTE FDD.

[Fig. 4] FIG. 4 is a schematic diagram showing a general structure of a subframe in a downlink component carrier defined for 3GPP LTE.

[Fig. 5] FIG. 5 is a schematic diagram illustrating the grouping of system information information items into system information blocks for different CE levels.

[Fig. 6] FIG. 6 is a schematic drawing illustrating an exemplary system information block structure for different CE levels.

[Fig. 7] FIG. 7 is a schematic drawing illustrating a comparison between legacy system information signaling and system information signaling for MTC.

[Fig. 8] FIG. 8 is a block diagram illustrating a receiving and transmitting apparatus.

[Fig. 9] FIG. 9 is a sequence diagram illustrating the reception and transmission method.

[Fig. 10] FIG. 10 is a schematic diagram illustrating transmission interleaving of different SIBs/SIs.

DESCRIPTION OF EMBODIMENTS

[0076] The present disclosure relates to the transmission and reception of system information in a wireless communication system, which is particularly suitable for the transmission and reception of system information for machine type communications such as MTC in 3GPP LTE. System information signaling has recently been discussed in 3GPP and there is prior agreement for the following purposes:

[0077] Support for flexibility similar to that offered by the current SIB concept, i.e. the size of the SIBs does not need to be fixed.

- branch from SIB1, ie the LC/EC of the UE receive a separate occurrence of the SIB1 and others (different time/frequency resources). The new SIB1 is common to EC and LC.

- transmission of SIB1 information separately from other SIBs (in particular in low cost UEs in normal coverage), if feasible in terms of overhead and total data acquisition time.

- scheduling information (time, frequency and MCS/TBS) enabling the LC/EC UEs to obtain SIB1 can, for example, be carried in the MIB, ie dynamic L1 information in the PDCCH is not needed.

- SIB1 for LC/EC UEs may contain scheduling information (time, frequency and MCS/TBS), allowing subsequent SIBs to be received without reading the PDCCH.

- A TB size limit of 1000 bits for broadcast may be acceptable, assuming that the network provides separate SIBs (different time/frequency resources) for LC/EC UEs and legacy UEs.

[0078] If the current mechanism for transmitting system information is applied to communication using a large number of repetitions, such as MTC communications, each of the SIBs currently used will be transmitted at about 50 times the repetition rate. In general, repetition rates can also be higher, such as greater than 200 repetitions. The number of repetitions can also be variable (configurable).

[0079] This will affect, for example:

- the data acquisition time for the system information by the legacy UEs if the system information blocks do not overlap, and thus the repetition of the system information will cause a longer delay in the transmission of the system information block and therefore also an increased delay in the transmission of the next system information block,

- retransmissions of all system information will also lead to a huge system load, which may be unnecessary, since MTC devices do not use all the information transmitted in the current system information signaling. Accordingly, the MTCs of the UE will receive irrelevant system information.

- Reception of all system information, which will increase the power consumption of the MTC device.

[0080] It is preferable to provide several possible levels of coverage improvement. However, any overhead that may result from additional signaling relating to different coverage enhancement levels may be critical, especially in view of the large number of repetitions that may be necessary for some of the coverage enhancement layers to transmit the information. Accordingly, it is preferable to provide efficient signaling regarding support for multiple coverage enhancement levels.

[0081] Preferably, the cell indicates which CE level(s) it actually supports. This indication may be broadcast in a cell within the system information so that the terminals are able to receive the information and decide whether to apply the corresponding CE layer operation.

[0082] For example, supported CE levels may be transmitted within system information and, in particular, within a Master Information Block (MIB) that is broadcast in the physical layer. In LTE, the MIB is transmitted over a physical broadcast channel that can be received and decoded by any terminal. However, the present disclosure is not limited to this, and broadcasting may be performed on a downlink shared channel. For example, CE levels may be indicated within SIB1. Still alternatively, the CE layers may be transmitted in another SIB whose location is also scheduled (eg, in MIB, or SIB1 or other specific SIB) to be reminded by blind decoding using SI-RNTI or RNTI specific to MTC operation.

[0083] Of the above possibilities, the transmission of CE levels within the MIB has the advantage that information about the CE levels is immediately available to terminals through physical broadcast. This increases the likelihood and reduces the delay in obtaining CE levels. On the other hand, in general, information signaled within the MIB should be minimized in order to use resources efficiently and avoid terminals reading broadcast information that is not necessarily important to them. On the other hand, signaling the CE levels in SIB1 provides the advantage that no additional blind discovery using the SI-RNTI or another RNTI of the group is necessary to find other SIBs. This is particularly advantageous for MTC terminals that may suffer from poor channel conditions (when located at a coverage edge in a cell) or that have a technically simple implementation and are expected to possibly use energy efficiently. Still alternatively, directly scheduled SIBs other than MIB or SIB1 may be used for CE layer signaling.

[0084] The different CE levels applicable for communication between the UE and the network depend on the support of the network and on the functionality of the UE. For example, a coverage extension of 5, 10, or 15 dB (or even more) may be supported and designated as low, medium, and high CE levels, respectively. Normal coverage may be referred to as zero coverage extension (0 dB), i.e., no extension.

[0085] Some information elements (IEs) carrying system information parameters may have the same value for different CE levels, while other IEs must have different/unique values among different levels. For example, some examples of SIBs of general meaning are typically SIBs such as ETWS/CM AS as briefly described above, and IEs such as different neighbor lists (intra-frequency, inter-frequency, inter-RAT, etc.) and ACBs, access class restriction, (cell level). Some examples of different/unique values among different cell CE levels are (re)selection parameters (such as q-RxLevMin, q-RxQualMin, etc.), PRACH parameters, and some others in the RadioResourceConfigCommon SIB3, EAB (SIB14) and etc.

[0086] For example, possible common values for qRxLevMin (in dBm) defined in the SIB for cell discovery/reselection for respective different CE levels are shown below:

q-RxLevMin_zero -60

q-RxLevMin_low -50

q-RxLevMin_med -40

q-RxLevMin_high -30

[0087] One of the purposes of the present disclosure is to provide efficient signaling and packaging of system information that may be common as well as different for different CE levels.

[0088] Signaling together system information related to all CE levels can lead to severe cell congestion. On the other hand, separate signaling for each CE layer may complicate the eNB scheduler and the behavior of the UE in acquiring and reacquiring system information on layer changes and SI change notifications.

[0089] One possible approach is to pack all information regardless of CE levels together, structured as in the legacy case, ie, no coverage improvement. In this approach, when needed, IE will have exactly as many values as the number of supported CE levels, that is, one per CE level. However, since CE-specific methods, such as the number of repetitions, may be different for each CE level, the above approach may lead to unnecessary system loading, as illustrated in the following calculation. Assume that the number of repetitions applied to each data block for zero, low, medium, high CE levels is 4, 10, 20, 50 repetitions, respectively, and the legacy SIBx size is 100 (bits).

[0090] If separate SIBs are transmitted for each CE layer, the corresponding number of required bits will be 4*100, 10*100, 20*100, and 50*100, resulting in a total overhead of 400+1000+2000+5000 =8400 bits. If, on the other hand, information elements for all CE levels are packed in the same system information block, this block must be repeated the maximum number of times, i.e., 50 times, resulting in a total overhead of 50*400=20000 bits. If a compromise is chosen and two system information blocks are used, each for two CE levels, the total overhead is reduced to 10*200 and 50*200, resulting in 2000+10000=12000 bits.

[0091] As can be seen from the above examples, the structuring and grouping of information regarding different levels of coverage improvement has a large impact on the transmitted overhead and thus also on the transmission efficiency.

[0092] As described above, it is preferable to provide CE levels supported in a cell via cell broadcast. The CE level indication can have different formats. For example, supported CE levels may be signaled explicitly (eg, in SIB1 or MIB or in another manner as mentioned above), for example, by enumerating them.

[0093] However, to save some signaling bits, only the highest supported CE layer can be signaled explicitly. A device receiving such indications signaling the highest supported CE level then assumes that all lower CE levels are also supported.

[0094] Still alternatively, CE levels may be indicated indirectly, for example, by broadcasting as many values of a specific parameter (eg, related to cell selection or cell reselection parameters, such as q-RxLevMin) as there are supported CE levels. To make the mapping unambiguous, the values are ordered in a predetermined manner, such as starting at a certain highest CE level and going down to lower levels, or starting at a certain lowest CE level and going up to higher levels, or in any other way.

[0095] In order to efficiently signal information elements for different CE levels, according to one exemplary embodiment, all IEs with different content (value) for different CE levels are grouped per CE level. For example, there is one SIB per CE level. The remaining IEs that have the same content (values) for all CE levels are grouped together in another single SIB common to all CE levels. This approach is illustrated in Fig. 5.

[0096] FIG. 5 illustrates at the top the transmission of information elements that have different content for different respective CE levels. The attribute "content" here indicates the values of specific parameters. The values don't have to be actually always different. Rather, what is meant is that they can be set to different values for different respective CE levels. As described above, values for different CE levels are preferably transmitted with different numbers of repetitions. In this example, values for different CE levels are also transmitted at different intervals, as appropriate.

[0097] In the case of different content shown at the top of FIG. 5, there are two different SI/SIB transmissions (cf. solid line and dotted line, respectively). The content illustrated by the solid line 510 here represents higher CE levels and is therefore transmitted more frequently than the content illustrated by the dashed line 520 which represents lower CE levels.

[0098] FIG. 5, "P1" denotes the first system information transmission period (frequency) for the first CE layer, which is higher than the second periodicity (frequency) indicated as "P2", for the SI transmission relating to the second CE layer lower than first level CE. It is assumed that a lower CE level means less coverage improvement, while a higher CE level means more coverage improvement (reception also possible at lower signal strength than for lower CE levels).

[0099] The bottom of FIG. 5 illustrates the transmission of information elements that have common content for different respective CE levels (5dB, 10dB and 15dB levels corresponding to "low", "medium" and "high" and denoted by different respective linetypes in the figure). In this "same content" case, the transmission period is determined according to the worst (eg 15 dB CE) extension (cf. "P1" in the figure). However, terminals supporting other CE levels (5dB, 10dB) may read (receive and store/attempt to decode) the SI less frequently, as illustrated by the arrows with different linetypes corresponding.

[0100] In order to conserve battery power in the wireless device, wireless devices (UEs) with better reception quality (ie, lower CE level) receive common content less frequently than it is transmitted.

[0101] It should be noted that a wireless terminal that has successfully received information after a certain number of repetitions less than the maximum number of repetitions may stop receiving the remaining repetitions.

[0102] Another strategy that these UEs may use is to accumulate and soft-combine receptions using all or most of the frequent transmissions and simply enter sleep mode after a successful reception. In other words, the wireless device tries to decode the system information after receiving each repetition, and once the decoding succeeds, the reception of additional repetitions is stopped. This strategy provides the advantage of obtaining system information as quickly as possible. For non-broadcast, eg, dedicated or unicast message(s), such as paging, the UE may even inform the network when stopped so that the network may stop additional (re)transmissions of the dedicated or unicast message(s). In other words, the wireless device may further comprise a transmission unit for transmitting to the network a notification of the complete reception of the system information.

[0103] Regarding the feature "repetition", this feature is not limited to bit repetition in the physical layer. Conversely, repetitions may be different versions of the redundancy, or, in general, different versions of the same system information content.

The concept of retransmissions and combining with HARQ has been described above in the Background section. However, the principles of transmitting a different version of coded data redundancy can be extended to any retransmission scheme without requiring any feedback from the receiver. In the case of system information that is broadcast for reception from a plurality of terminals, no feedback schemes are used. However, instead of providing just repetitions of the system information, it is preferable to transmit different redundancy versions in order to increase the combining gain. Thus, also one exemplary embodiment of the present disclosure, combinable with any other embodiments of this disclosure, includes transmitting different versions of coded system information redundancy (i.e., different pieces of coded system information) similar to retransmissions as described above for HARQ and as used in the current LTE/LTE-A standard. Combining may also work in the same way, eg incremental redundancy combining, possibly together with soft combining of different repetitions of transmitted redundancy versions).

[0104] In other words, in the "same content" case, there is only one content transmission (SI/SIB), but the receiving UEs receive the content at a frequency (appropriate periodicity) based on their respective CE operating level.

[0105] For example, UEs configured with 5 dB CE level will only receive common content 5 times in a given time period, on the other hand, UEs configured with 10 dB CE level will receive common content twice as often, i.e., 10 times in a given period of time. Moreover, UEs configured with 15 dB CE level will additionally receive common content more frequently, eg, twice as often as 10 dB UEs (ie, 20 times in this example).

[0106] The given period may correspond to a system information window or a plurality thereof, which is a time domain interval in which one system information message (SI message as in the legacy system described above) and their respective repetitions are transmitted.

[0107] In practice, having as many SIBs as CE levels can be difficult to adopt, as it represents a very different approach from a legacy system where grouping is primarily based on logical intent/usability. Moreover, providing separate SIBs for all respective individual CE levels can add complexity to scheduling and notification of SI changes, with the scheduler now having to take care of 4 times as many SIBs/SIs corresponding to the four CE levels. When an IE that has a different value for each of the CE layer changes, then a change notification must be sent to the related UEs. Since the respective UEs need different CE support even to receive the SI change notification, this adds additional burden to the eNB scheduler.

[0108] Accordingly, it may be preferable to keep the legacy system unaffected by updates to the MTC-specific SIBs. A new, separate new value tag or tags may thus be provided to signal to wireless devices that system information regarding MTC operation and in particular CE operation has changed. The new value tag can be separate for the "miscellaneous content" group and for the "general content" group. Moreover, the new value tag can be specific and separate for each CE level or for each group of CE levels (eg groups A and B, as described below). The type of change may also be signaled within a page message that is sent from the network to wireless devices to notify them of a change in system information. The type of change may indicate the CE level for which the SI has changed and/or whether the change concerns IEs common to all CE levels or IEs specific to each level.

[0109] The modification period (the smallest period of time after which the SI can change) can also be set differently and independently for the "common content" and "miscellaneous content" system information. In addition, the change period may also be set differently for different respective CE levels or CE level groups.

[0110] It should be noted that different SI/SIBs can also be transmitted in an interleaved manner, as illustrated in FIG. 10. In particular, as can be seen from the three diagrams (a), (b), and (c), there are at least three ways to perform SI transmission with or without SI/SIB interleaving. In the first scheme (a), the maximum number of transmissions for the SIB/SI is made and then the transmission for the next one SIB/SI is started. This is a non-interleaved scheme.

[0111] In the second scheme (b), SIB/SI are interleaved and transmission is performed once every 20 ms period. This scheme should further benefit from time diversity and likely fewer transmissions than would be required for the maximum number of transmissions for SIB/SI in the first scheme.

[0112] With regard to receiver behavior, two schemes are possible. Scheme A is to have more than one HARQ process (as many as the number of interleaved SIs - 2 in this example).

Then, after one cycle of the SI transmission period, the UE may receive multiple SIs at the same time. Scheme B is that the receiver has only one HARQ process and only to receive one SI during one SI transmission period. To receive "n" SIs, the UE must receive "n" cycles of SI transmission periods.

[0113] This scheme B can be applied by the receiver regardless of whether interleaving is applied by the network.

[0114] In the third scheme (c), only the corresponding SIB/SI transmissions are extended by 20 ms; while the broadcast takes place every 10 ms (in case of 2 SIB/SI interleaving).

[0115] The table below makes a comparison between the three schemes.

[0116] [Table 2]

Advantages Flaws Scheme 1 of Fig. 10(a) Requires one HARQ process/buffer in MTC devices
Good in terms of broadcast overhead (5%=1/20) May require slightly more gears than 2A. Scheme 2 of Fig. 10(b) Best in terms of broadcast overhead (<5%) Scheme A: Requires more than one HARQ process (as many as the number of interleaved SIs)
Pattern B: Longest time required to receive multiple SIs. Scheme 3 of Fig. 10(c) The fastest complete system information retrieval Requires more than one HARQ process (as many as the number of interleaved SIs)
The prospect of doubling broadcast overhead (10%)

[0117] Given the delay-tolerant nature for MTC application, schemes (a) and (b) seem to be preferred. If low complexity/cost prevents more than 1 HARQ buffer for broadcast, then scheme (a) is preferred, which also supports the legacy SI non-overlapping window principle. However, from a coverage extension point of view, scheme (b) may be more appropriate. It should be noted that the above example only shows the interleaving of 2 different SIBs (system information). However, in general, interleaving can also be performed for any other number of SIBs. As mentioned above, interleaving is similar to the concept of HARQ processes even if there are no feedback based retransmissions in the case of a SIB/SI block. However, repetitions/versions of the same SIB/SI can be considered as retransmissions of the same data.

[0118] Moreover, in general, one particular SI may have one particular modification boundary and another will have another particular modification boundary, and the two may overlap. The modification boundary here indicates a point in time up to which the system information will not change, but only from the start of the next modification period.

[0119] In general, the transmission of a plurality of N (N>1 is an integer) types of system information can be interleaved, which means that N different system information (SIBs) are transmitted cyclically a predetermined number R of repetitions/versions (R is an integer , greater than 1). According to one embodiment, there are only two groupings of the same IEs for two corresponding EC layer groups. But the border of the two groupings can be flexible, for example, as shown in the following.

1) the first grouping "Grouping-A" for zero level CE and the second grouping "Grouping-B" for low, medium, and high level CE

2) the first grouping "Grouping-A" for zero and low level CE and the second grouping "Grouping-B" for medium and high level CE

3) the first grouping "Grouping-A" for zero, low, and medium levels of CE and the second grouping "Grouping-B" for high level CE

4) only one grouping, which is the same regardless of the CE level (zero, low, medium, high)

[0120] For example, the applicability of the above configurations 1) to 4) may be signaled within the system information carried by SIB1 or SIB carrying scheduling information (as will be illustrated below with reference to FIGS. 6 and 7).

[0121] Moreover, Grouping-A may be indicated by a separate SIBx-A (x stands for any SIB such as SIB1 or SIB, etc. e.g. SIB2-A stands for SIB2 for group A) and Grouping-B may be indicated by means of a separate SIBx-B different from SIBx-A. The number of repetitions (and/or redundancy versions) may be different between SIBx-A and SIBx-B. Preferably, SIBx-A and SIBx-B are carried in their respective separate SI messages (separately). Their planning can also be independent. The number of repetitions (versions) may also differ between SIBx-A and SIBx-B and depend on the contained CE levels.

[0122] SIB1 or scheduling information (when signaled) may also indicate additional scheduling details of the SIBx-A and SIBx-B block, such as frequency position (PRB start and/or end, subframe pattern or time domain-specific positions, hopping flag frequencies, etc.

[0123] It should be noted that the above interleaving, as shown in FIG. 10 may be applied to different groups as described above. Fig. 10 shows the overlap of 2 different SIBs. These SIBs may be SIBx-A and SIBx-B as illustrated above, that is, SIBs carrying different CE layer groupings. Alternatively, or in addition, interleaving (as shown by dashed and solid lines in FIG. 10, diagrams (b) and (c)) can be performed between "common content" SIs and between CE-specific SIBs.

[0124] The above example described with reference to FIG. 5 shows that the frequency with which the CE-specific information is transmitted can also be CE-specific, that is, different for at least two different CE layers. In other words, IEs specific to each CE level may be grouped for each corresponding CE level. For example, one SIB may include IEs from only one CE layer. Alternatively, in general, IEs specific to each CE level may be grouped across multiple CE levels. For example, one SIB may include IEs from two or more CE levels. It should be noted that this can also be done by providing IEs with two or more values for corresponding two or more CE levels. Specifically, in the case where multiple CE layers are grouped and transmitted at the same frequency, the other receiving terminal may be configured to receive IEs at a frequency lower than the frequency at which those IEs are transmitted. This approach may help reduce the power consumption of the terminal.

[0125] For example, suppose a case in which IEs from two CE levels (middle and high) are transmitted at the first frequency corresponding to the high CE level, so that wireless devices using the high CE level are also capable of receiving this system information. Assume that the wireless device applies a medium CE layer. This wireless device does not necessarily need to receive all transmissions, and to conserve battery power, it can be configured to receive IEs less frequently than provided by the first periodicity.

[0126] In the above example, it is assumed that there is a certain period of time in which the transmission of system information regarding different CE levels and including repetitions should be performed. Therefore, a certain period of time corresponds to the maximum time in which the acquisition of system information can be performed. The number of repetitions for different CE layers is different, which results in this case different transmission rates of IEs (SIBs) for different CE layers.

[0127] However, the present disclosure is not limited to this approach. In general, the number of repetitions may vary without requiring that they be kept within the same time period. Thus, the periodicity (frequency) of transmission of system information corresponding to different CE levels can remain the same. This means that the maximum time to obtain system information for the CE level currently in use will depend on that CE level.

[0128] The following describes an exemplary operation of the system information receiving apparatus. This may be a wireless device such as a terminal (UE) of any form, such as a mobile phone, smartphone, tablet, laptop, PC, wireless card, USB-connected receiver, or any other device.

[0129] A wireless device supporting coverage enhancement may first determine its CE level. The determination of the appropriate level may be performed, for example, based on path loss calculations and/or cell measurements or the like. Then, the wireless device checks if the cell in which it is located supports a certain CE level. This verification is performed by receiving broadcast information including the CE level indication. The CE level indication may be received in, for example, MIB or SIB1 or another SIB as described above. It can be signaled implicitly by considering the number of passed values (instances) of one of the parameters (out of many such possible candidates), as described previously. Based on the received CE level indication, the wireless device determines whether the desired CE level is supported in the network. The UE may determine the 'required' CE level in terms of the time/effort required to acquire a cell, or in terms of the time/effort required to receive a MIB or some other SIB, or even a reception quality such as RSRP (Received Reference Signal Power) or RSRQ (received reference signal quality), or even using path loss estimation (the greater the path loss, the higher the required CE level). Based on the set CE level, the wireless device determines its interest/need to receive the SI, that is, whether the "different content" type or the "same content" type should be received and with what frequency. This determination may be based, for example, on the behavior defined in the specification and/or based on scheduling information. In particular, the scheduling of common SIBs and/or CE-specific SIBs may be determined by scheduling information carried within system information, such as MIB or SIB1 or another SIB. Alternatively, scheduling may be subject to some rules defined in a specific instance of the standard and may require blind discovery using a group RNTI such as MTC-specific MTC-RNTI, or a generic SI-RNTI for system information, or an EC-RNTI specific to coverage improvement. or for a specific CE level.

[0130] Next, the wireless terminal obtains the corresponding scheduling information and, thereafter, the intended SI (required and according to its own defined CE layer) by activating to receive the SI only according to its scheduling (regardless of transmission frequency).

[0131] Devices that do not support CE can additionally operate as a legacy system (the current LTE standard), that is, operate normally in good coverage; or declare yourself out of service in poor/extended/missing coverage.

[0132] FIG. 6 illustrates an example of obtaining system information according to one embodiment. In particular, the network advertises the supported CE levels implicitly or explicitly as described above, i.e., by including the CE levels explicitly in the information broadcast in the cell, or by deriving the CE levels from other parameters broadcast in the cell.

[0133] Next or before this step, the wireless device discovers its current CE level. This can be done, for example, based on the calculation of path loss (and/or RSRP, received power of the reference signal, or measurements of Q, such as the reception quality of the reference signal, RSRQ).

[0134] The following are examples of conditions that may be used to determine the current CE level of a wireless device:

1) if x < Path loss, then the CE level is defined as high

2) if y < Path loss < x, then the CE level is defined as the average

3) if z < Path loss < y, then the CE level is defined as low

[0135] Under the above conditions, the following inequality x > y > z holds and the parameters x, y, and z are thresholds for path loss that can be broadcast within the system information, for example, in the MTC SIB1 or in the MIB or in another SIB.

Alternatively, similar conditions may be formulated for RSRP or RSRQ, or for any other measured variables reflecting channel conditions, and appropriate thresholds may be declared by the network or defined within the standard.

[0136] After determining its own CE level, if the determined CE level is supported by the network, the wireless device (MTC) obtains the system information "Miscellaneous Content" and "Common Content" for its determined CE level, as illustrated in FIG. 6.

[0137] Reception of system information related to a certain CE layer can be achieved by receiving scheduling information that is transmitted by the network within a cell. In particular, the scheduling information may be broadcast as part of the SIB1. However, the present disclosure is not limited to this, and scheduling information for system information regarding different CE levels may also be provided within an isolated system information block. To keep complexity low, such an isolated system information block may be directly scheduled from SIB1 (or MIB). However, these are only examples and, in general, system information for specific CE levels may be scheduled in another way, such as in a MIB or in a system information block that needs blind discovery.

[0138] FIG. 6 illustrates an exemplary grouping of information elements related to different CE levels. In particular, the common content, which is the same for all possible CE levels, may include SI-3 and SI-4 system information messages. System information messages are (in LTE terminology) RRC protocol messages, each of which may include one or more system information units, as described above in the Background section. In the present example, the system information message SI-3 includes two system information blocks, namely SIB-M and SIB-(M+1). On the other hand, the system information message SI-4 includes two other information blocks, namely SIB-(M+2) and SIB-(M+3). However, this is just an example, and the common content structure may also include one single system information message carrying a single one or a plurality of system information blocks. System information blocks usually group elements with a similar purpose (cf. the Prior Art section above).

[0139] System information that is different for different CE levels (cf. "different content" in FIG. 6) is also illustrated in FIG. 6. Accordingly, there are two different system information messages SI-1 and SI-2 for each of the four CE levels "zero", "low", "medium", and "high". The system information message SI-1 includes two system information blocks, namely SIB-N and SIB-(N+1). In general, a system information message may also include one single SIB or more than two SIBs. The SI-2 system information message includes only one system information block, designated as SIB-(N+2), which is also illustrative only. As can be seen from this example, the system information for each of the different CE levels here has the same structure in terms of system information messages and system information blocks. Accordingly, the values of the information elements carried in the respective SIBs for different CE levels may be set independently, and thus may have different values. The information elements that are common to all CE levels are in this example organized independently and in a different manner from the "miscellaneous content" system information. In particular, "common content" includes system information messages and also system information units other than those included in the "miscellaneous content" system information.

[0140] However, it should be noted that this is not meant to limit the present disclosure of system information by such an entity. Rather, some parts of the same SIB may be carried within a "miscellaneous content" section, while other parts of the same SIB may be carried within a "common content".

[0141] The system information structure illustrated in FIG. 6 may exist in parallel system information to be read by a legacy wireless device for system information defined by the current LTE standard.

[0142] FIG. 7 illustrates a comparison between the system information structure currently applied in LTE and the system information structure according to the preferred embodiment. The left side shows the legacy structure. In particular, most of the Information Block (MIB) is transmitted in a broadcast manner on a broadcast physical channel. SIB1 scheduling is fixed in the time domain and the UE performs blind decoding using SI-RNTI on these particular time instances (subframes) to find the frequency location of the SIB1 block. SIB1 then includes scheduling information for system information messages SI-1, SI-2, SI-3 carrying additional system information blocks.

[0143] SystemInformationBlockType1 (SIB1) uses fixed scheduling with a frequency of 80 ms and repetitions done within 80 ms. The first transmission of SystemInformationBlockType1 is scheduled in subframe #5 of radio frames for which SFN mod 8=0, and repetitions are scheduled in subframe #5 of all other radio frames for which SFN mod 2=0. A single SI-RNTI is used to address SystemInformationBlockType1 as well as all SI messages.

[0144] The system information structure of the present embodiment, which is particularly suitable for the MTC LC/EC mode, is shown on the right side of FIG. 7. The MIB is the same as the MIB used for the legacy system (on the left side). However, some bits that have been reserved in the MIB, as defined in the current LTE standard, are used here to carry information about location (within the resource grid), periodicity, frequency hopping, and/or TBS (transport block size), etc. . block SIB1. In this example, SIB1 (MTC-SIB1) is specific to MTC LC/EC and differs from legacy SIB1 (in general, resources for SIB1). The MTC-SIB1 in this example further points to a separate SIB including scheduling information for SIBs common to different CE layers and scheduling information for SIBs different to different CE layers. In particular, the scheduling information indicates the location of the system information message SI-2 and the system information message SI-3. The system information message SI-1 may be directly indicated from the MTC-SIB1.

[0145] However, the present disclosure is not limited to this example. For example, the legacy system SIB1 may also be reused instead of providing a separate MTC-specific SIB1. Moreover, SIB1 (legacy or MTC-specific) may also only point to scheduling information and not to other system information messages/blocks. The scheduling information will then carry all the information regarding the scheduling of the system information for the different CE levels. In the example above, the scheduling information is part of a separate system information block. However, the system information block may also include additional information regarding the MTC and/or different CE levels. For example, it could include system information common to all CE levels and systemInfoValueTag for all system information separately for each CE level, or even multiple systemInfoValueTags, one for each functionality/procedure/SIB, etc. for each CE level or for all CE levels grouped together.

[0146] Alternatively, the scheduling information may be included directly in SIB1 (or MTC-SIB1).

[0147] The embodiments and examples disclosed above may provide various advantages. For example, cell support for any particular CE layer is visible to the wireless device, and the wireless device can also calculate its own required coverage extension. Moreover, the load of the cell/system is limited to a reasonable limit by the above-described structure (grouping) of system information related to coverage improvement. The implementation and/or behavior of an eNB scheduler (generally, a network node scheduler that conveys system information) is not complicated. Moreover, legacy UEs (wireless devices that do not support coverage enhancement, such as LTE and LTE-A devices supporting Releases 8 to Release 13) are not affected. The behavior of the MTC device in receiving, reacquiring on layer changes and on SI change notifications is clear.

[0148] The present disclosure provides an apparatus 800A for receiving system information in a wireless communication system supporting coverage improvement as shown in FIG. eight.

[0149] This device can be any wireless device, such as any type of user device (terminal), such as a mobile phone, smartphone, tablet, computer, computer card, or USB-attached wireless interface, or the like.

[0150] The device preferably includes a receiving unit 820 for receiving system information; a control unit 810 for controlling the receiving unit to receive system information including coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system; and for receiving system information including a group of information elements common to different coverage enhancement levels and one or more groups of information elements specific to different grouped coverage enhancement levels.

[0151] The grouping of CE-specific information can be performed for the respective CE levels (or groups of CE levels). For example, the grouping here may be performed on a system information block basis such that a separate SIB is provided for each CE level (or for a subset of CE levels) and another separate SIB is performed for IEs common to all CE levels. Alternatively, the grouping may be performed on an information element basis, that is, each IE includes the respective values for the respective CE levels. Other groupings are also possible, including mixing the aforementioned SIB based and IE based approach.

[0152] For example, system information is transmitted in system information blocks; and a group of information elements common to different coverage enhancement levels is transmitted in a system information block different from the system information block in which information elements specific to at least one other coverage enhancement layer are transmitted.

[0153] The information elements for the first coverage improvement level are received at a repetition rate higher than the number of repetitions with which the information elements for the second coverage improvement level are received, with the first coverage improvement level being higher than the second coverage improvement level.

[0154] This arrangement ensures that terminals having poorer channel states (corresponding to a higher CE level) can receive more SI repetitions to increase the probability of correctly receiving SI (correct decoding).

[0155] According to one embodiment, the group of information elements common to different coverage enhancement layers is transmitted at a first frequency, and the control unit is configured to control the receiving unit to receive versions of the group of information elements common to different coverage enhancement layers at a frequency equal to or less than the first frequency, depending on the level of coverage improvement currently applied by the device.

[0156] Thus, terminals applying different coverage enhancement levels can read SI at different rates and thus improve the trade-off between battery power and SI acquisition time rate. However, the present disclosure is not limited to this arrangement. Rather, each terminal may read all repetitions (versions) of the SI and stop receiving once the SI has been successfully decoded. Other embodiments are possible, for example, wireless devices of different CE levels may be configured to receive only a certain number of repetitions (versions).

[0157] The received coverage improvement level indication may comprise at least one of:

- a list of supported coverage enhancement levels,

- the highest supported coverage enhancement level, wherein the device is configured to output supported coverage enhancement levels as all levels less than or equal to the received highest supported coverage enhancement level, or

- the number of values of a particular information element, wherein the device is configured to output supported coverage enhancement levels according to the number of values of a particular information element, or

- a single information element value, wherein the device is configured to output supported coverage enhancement levels according to the single information element value.

[0158] Accordingly, the coverage enhancement levels supported by the network may be advertised either explicitly by broadcasting the relevant system information in MIB, SIB1 or another SIB) or implicitly by indicating the CE levels supported, for example, by the number of values of a particular information element ( elements), or even by specifying M-SIB1 periodicity (higher M-SIB1 periodicity means the highest CE level supported; M-SIB1 medium periodicity means the average CE level supported, and so on) or even by associating, for example, possible starting positions of M- SIB1 with specific levels of CE support (initial position [say PRB index] for M-SIB1=X would mean high CE level support; initial position [PRB index] for M-SIB1=Y would mean medium CE level support; and so on ). As an example for periodicity, let's say CE high, medium, low has 20, 60 and 100 as periodicity. Then, when the MIB indicates the periodicity as 20, the UE knows that the periodicities of 60 and 100 are also supported, that is, the medium and low CE levels are also supported when the CE high level is supported.

[0159] Thus, regarding indication by a single information element value, it may be for an information element indicating a periodicity (frequency of occurrence). For example, the CE level high, medium, and low may have 20, 60, and 100 ms as periodicity. Then, when the MIB indicates the periodicity as 20, the UE knows that the periodicities 60 and 100 are also supported, that is, the CE levels medium and low are also supported when the CE level "high" is supported.

[0160] In particular, the control unit may control the receiving unit to receive system information in multiple versions.

[0161] Here, the version flag may denote redundancy versions or any other type of content repetition. For example, SI may be encoded with forward error coding, which adds redundancy. Examples of such coding may be turbo codes or convolutional codes as used in LTE. However, any other coding is also possible, such as block codes such as LDPC, BCH, or the like. One version of such an encoded SI then corresponds to a portion of the encoded SI. Different parts - versions - of the encoded SI may be transmitted at different times (eg, in different subframes). These parts may be individually decodable.

[0162] However, the SI versions can also be simple repetitions or a combination of redundancy versions and their repetitions. For example, there may be four (in total K, where K is an integer greater than 1) redundancy versions defined for each SI message, and these four RV versions are transmitted cycling through a plurality of times (in total, N, where N is an integer greater than 1). The SI versions may be mapped to corresponding subframes.

[0163] The apparatus may further comprise a combiner for combining the plurality of received versions and a decoder for checking whether the system information after combining can be correctly decoded; and the control unit is configured to prevent the receiving unit from receiving additional versions of the system information if the system information after combination can be correctly decoded.

[0164] The combining unit may include, for example, a soft combining module that combines the detected bit reliabilities of the received versions/repeats, or a hard combining module that combines the detected bits. Combining may include incrementally combining the redundancy of different redundancy versions into one coded block, which is then decoded.

[0165] Moreover, the combiner is preferably configured to combine a plurality of system information versions received so far after each version is received, and the decoder is configured to check whether the system information can be correctly decoded after each combination.

[0166] Upon receipt of each new SI version, combining may be performed and decoding may be attempted. However, an attempt may also be made to decode the new received version of the SI individually first and combine only if it is not correctly decodable. The correctness of the decoding can be checked by checking the cyclic redundancy check (CRC) attached to the SI. However, other embodiments are also possible without limiting the present disclosure. For example, decoding may be attempted not after receiving each new SI version, but rather after receiving (and possibly combining) every M (M is an integer greater than 1) SI versions to reduce computational complexity.

[0167] According to one embodiment, the device further comprises a coverage enhancement level determination unit for determining its own coverage enhancement level based on one of the path loss, the received power of the reference signal, and measurements such as the reception quality of the reference signal, and for checking whether whether the determined native coverage enhancement level is supported by the wireless communication system, based on the received coverage enhancement level indicator, wherein the control unit is configured to, if the native coverage enhancement level is supported by the wireless communication system, control the receiving unit to receive system information for the native coverage enhancement level.

[0168] If the native coverage enhancement layer is not supported by the current cell network, then the terminal may attempt to change the cell (via cell reselection) or be out of network coverage. However, other behavior can also be defined.

[0169] The control unit may be configured to control the receiving unit to receive scheduling information within the system information block indicated from the system information block (SIB1) whose location is indicated in the main information block (MIB); and for receiving system information for the own coverage improvement level according to the scheduling information.

[0170] This is only a preferred example of scheduling SIBs in which the SI related to the CE is transmitted. In general, scheduling may be performed in various ways, for example, by direct reference to scheduling information from the MIB, or by any other method. The scheduling information may completely define the resources in which the CE-common and CE-specific SI information is transmitted. This has the advantage of being simple to implement a terminal that simply accepts the SI in the resources specified in the scheduling information. However, complete scheduling information (including time and frequency domain resources, frequency hopping, transport block size (TBS) and modulation and coding scheme (MCS), etc.) may also introduce significant signaling overhead. Alternatively, the scheduling information may only include a subset of the resource specification while other resource characteristics are fixed. For example, the frequency location of the SI information may be fixed for the central 6 PRBs or for any other subset of frequency resources. Alternatively or in addition, the frequency hopping application may be fixed or signaled in a different, less frequent manner (in a different SI) and the TBS and/or MCS may be fixed or signaled elsewhere. The time domain scheduling may include (or consist of) specifications of subframes in which the SI is to be carried. The scheduling information preferably includes separate scheduling for individual groupings of IEs - a CE level independent group (IEs common to all CE levels) and for specific corresponding groupings specific to one or more CE levels.

[0171] For example, the coverage enhancement level indication may indicate one or more of four different coverage enhancement levels, including a zero level indicating no coverage improvement.

[0172] However, the number four is only illustrative and may be preferred as it requires only 2 bits of signaling and still distinguishes between three levels of CE and no CE.

[0173] System information for different coverage enhancement levels is grouped according to one of the following configurations:

- the first group for the zero level and the second group for the remaining three levels of coverage improvement;

- the first group for the zero level and the smallest of the four levels of coverage improvement and the second group for the remaining two levels of coverage improvement:

- the first group for the zero level and two lower levels of coverage improvement and the second group for the highest of the four levels of coverage improvement; and

- one single group for all four coverage enhancement levels, and

the control unit controls the receiving unit to receive the configuration currently used by the network within the system information.

[0174] It should be noted that the above examples show four levels of CE, also including a zero level. However, it should be noted that level zero should not be included as a separate CE level. For example, the general use of EC may be signaled or implicitly indicated elsewhere.

[0175] However, the zero level may mean that MTC is applied, but without EC, for example, only the LC mode.

[0176] The system information may be a MIB, SIB1, scheduling information SIB, or any other SIB in general, as described above.

[0177] The configuration may be received within the system information message, further comprising a grouping of scheduling information indicating the location of the first system information unit in which the first group is transferred, and the location of the second system information unit in which the second group is transferred, wherein the first and second system information units information are mutually different.

[0178] For example, the wireless communication system is 3GPP Long Term Evolution, LTE, or LTE Evolved, LTE-A, and system information messages including system information blocks to support improved coverage, except for the main information block, are received regardless of the system information for LTE or LTE-A without coverage enhancement support.

[0179] Moreover, the present disclosure provides device 800B as shown in FIG. 8 for transmitting system information in a wireless communication system supporting coverage improvement.

[0180] This device 800B may be, for example, a network node controlling the transmission of system information within a cell. In particular, the network node may be a base station such as NodeB/eNodeB in UMTS and LTE (LTE-A, respectively).

However, the present disclosure is not limited thereto, any other device, such as a repeater or any node on a wireless network transmitting system information, may implement device 800B.

[0181] Device 800B may include: a transmission unit 870 for transmitting system information; a control unit 860 for controlling a transmission unit for transmitting system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system; and for transmitting system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0182] In particular, as shown in FIG. 8, device 800B may be configured to generate and transmit system information that is scheduled, grouped, and/or structured as described above in conjunction with receiving system information.

[0183] Methods for receiving and transmitting system information are illustrated in FIG. 9.

Accordingly, the present disclosure provides a method 900A for receiving system information in a wireless communication system supporting coverage enhancement, comprising the steps of: receiving 930 system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system; and receiving 980 system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0184] Method 900A may also include additional steps already described above, performed by various blocks of the respective receiver. In particular, FIG. 9 shows step 910 of determining a wireless device's own CE level (CEL). The determination of the CE level may be performed based on the measured channel quality, as illustratively described above. Then, the wireless device receives 930 the CE levels supported by the network and, in particular, the cell in which the wireless device is located (connected to). It should be noted that steps 910 and 930 can also be performed in reverse order. The wireless device then compares 940 the determined native CE level and the CE levels supported by the network to determine if its own CE level is supported by the network. In the case where the own defined CE level is not supported by the network, the wireless device is out of coverage of the current cell for which the system information was analyzed. If the native CE layer is supported by the network, at step 960, the wireless device receives system information scheduling information that indicates the resources in which system information regarding different CE layers is transmitted. Based on the scheduling information, in step 980, the wireless terminal receives system information regarding its own determined CE layer. Transmission and reception of system information is performed via the wireless interface 990.

[0185] Additionally, the present disclosure provides a method 900B for transmitting system information in a wireless communication system supporting coverage enhancement, comprising the steps of: transmitting 920 system information including a coverage enhancement level indication for indicating enhanced coverage levels supported by the wireless communication system; and transmitting 960 system information including a group of information elements common to different coverage enhancement levels and information elements specific to different coverage enhancement levels grouped for respective coverage enhancement levels.

[0186] This method is also illustrated in FIG. 9. Basically, a network node transmitting system information performs step 920 of broadcasting a CE level indication. The various possibilities for formatting the CE level indication have already been described above with reference to the respective receiver. The network node also preferably transmits 950 scheduling information specifying on which resources the system information regarding specific CE levels is transmitted. Finally, system information regarding specific CE levels is transmitted at step 960. Scheduling and formatting as well as grouping system information and related data (scheduling information and the like) are also described above in various examples and embodiments.

[0187] In accordance with another embodiment, there is provided a computer program product comprising a computer-readable medium having a computer-readable program code embodied thereon, the program code being configured to perform the present disclosure.

[0188] Other exemplary embodiments relate to implementing the various embodiments described above using hardware and software. In this connection, a user terminal (mobile terminal) and an eNodeB (base station) are provided. The user terminal and the base station are configured to perform the methods described herein, including appropriate entities for participating in the methods in an appropriate manner, such as receiver, transmitter, processors.

[0189] Additionally, it should be understood that various embodiments may be implemented or performed using computing devices (processors). The computing device or processor may, for example, be general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, and so on. Various embodiments may also be performed or implemented by a combination of these devices.

[0190] Additionally, various embodiments may also be implemented by software modules that execute by means of a processor or directly in hardware. A combination of software modules and hardware implementation may also be possible. Program modules may be stored on any type of computer-readable storage media such as RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROMs, DVDs, and so on.

[0191] It should be further noted that the individual features of different embodiments may individually or in an arbitrary combination be the essence of another embodiment.

[0192] One of skill in the art should appreciate that numerous changes and/or modifications may be made with the present disclosure as shown in specific embodiments. The present embodiments, therefore, are to be considered in all respects as illustrative and not restrictive.

[0193] In summary, the present disclosure relates to transmitting and receiving system information, which includes transmitting and/or receiving control for transmitting and/or receiving system information, including a coverage enhancement level indication for indicating enhanced coverage levels supported by a wireless system. communication, and for transmitting and/or receiving system information including a group of information elements common to different coverage enhancement levels, and information elements specific to different coverage enhancement levels, grouped for respective coverage enhancement levels.

Claims (44)

1. A device for transmitting system information in a wireless communication system that supports coverage enhancement, comprising: a control scheme that, in operation, generates system information including information elements common to different coverage enhancement levels and one or more information elements specific to different coverage enhancement levels, and a transmitter that, during operation, transmits the generated system information at a predetermined frequency. 2. The device according to claim 1, in which system information is transmitted in system information blocks; and information elements common to different coverage enhancement levels are transmitted in a system information block different from the system information block in which information elements specific to at least one other coverage enhancement layer are transmitted. 3. The apparatus of claim 1, wherein the predetermined frequency is different for transmitting information elements common to different coverage enhancement levels and transmitting information elements specific to at least one other coverage enhancement layer. 4. The apparatus of claim 1, wherein a group of information elements common to different coverage enhancement levels is transmitted at a first periodicity, and the control scheme controls the transmitter to transmit versions of a group of information elements common to different coverage enhancement levels at a frequency equal to or less than the first frequency, depending on the coverage enhancement level currently used by the device. 5. The device according to any one of paragraphs. 1-4, wherein the device transmits a coverage enhancement level indication that comprises at least one of: - a list of supported coverage enhancement levels, - the highest supported coverage enhancement level, where the coverage enhancement level indication enables the supported coverage enhancement levels to be output as all levels less than or equal to the transmitted highest supported coverage enhancement level, or - the number of values of a particular information element or a single information element value, wherein the device is configured to derive supported coverage enhancement levels according to the number of values of a particular information element or from a single information element value. 6. The device according to any one of paragraphs. 1-5, in which a control circuit controls the transmitter to transmit system information in multiple versions; while many versions provide the receiving device with the ability to: softly combine many passed versions and decode to check whether the system information after combination can be correctly decoded; and prevent the receiving device from receiving additional versions of the system information if the system information after combination can be correctly decoded. 7. The device according to any one of paragraphs. 1-6, in which the coverage improvement level is determined by the receiver based on one of the path loss, the received power of the reference signal, and measurements such as the reception quality of the reference signal, and whether a certain coverage improvement level is supported by the wireless communication system is checked by the receiver. device based on the transmitted coverage improvement level indication, wherein the control circuit, if the determined level of coverage improvement is supported by the wireless communication system, controls the transmitter to transmit system information for the determined level of coverage improvement. 8. The apparatus of claim 7, wherein the control circuit controls the transmitter to transmitting scheduling information within a system information block referenced from a system information block (SIB1) whose location is indicated in the main information block (MIB); transmitting system information for a certain coverage improvement level according to the scheduling information. 9. The device according to any one of paragraphs. 4-8, wherein the coverage improvement level indication indicates one or more of four different coverage improvement levels, including a zero level indicating no coverage improvement; system information for different coverage enhancement levels is grouped according to one of the following configurations: - the first group for the zero level and the second group for the remaining three levels of coverage improvement; - the first group for the zero level and the lowest level of the four levels of coverage improvement and the second group for the remaining two levels of coverage improvement: - the first group for the zero level and the two lower enhancement coverage levels and the second group for the highest of the four coverage enhancement levels; and - one single group for all four coverage enhancement levels, and the control circuit controls the transmitter to transmit the configuration currently used by the network within the system information. 10. The apparatus of claim 9, wherein the configuration is transmitted within the system information message, further comprising a grouping of scheduling information indicating the location of the first system information unit in which the first group is transferred, and the location of the second system information unit in which the second group is transferred, when In this case, the first and second system information blocks are mutually different. 11. The device according to any one of paragraphs. 1-10, in which the wireless communication system is 3GPP Long Term Evolution Project, LTE, or LTE-Advanced, LTE-A, system information messages including system information blocks to support enhanced coverage, excluding the main information block, are received regardless of the system information for LTE or LTE-A without support for coverage improvement. 12. A method for transmitting system information in a wireless communication system supporting coverage enhancement, comprising the steps of: generating system information including information elements common to different coverage enhancement levels and one or more information elements specific to different coverage enhancement levels; and, transmission of the generated system information at a specified frequency. 13. An integrated circuit that, in operation, controls a process in a device for receiving system information in a wireless communication system supporting coverage enhancement, the process including: receiving system information to indicate the level of coverage improvement; and while receiving system information includes information elements common to different levels of coverage improvement, and one or more information elements specific to different levels of coverage improvement, transmitted at a given frequency. 14. An integrated circuit that, in operation, controls a process in a device for transmitting system information in a wireless communication system supporting coverage enhancement, the process including: generating system information including information elements common to different coverage enhancement levels and one or more information elements specific to different coverage enhancement levels, and transmission of the generated system information at a specified frequency.

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