WO2018063063A1

WO2018063063A1 - Partitioning of random access resources

Info

Publication number: WO2018063063A1
Application number: PCT/SE2017/050936
Authority: WO
Inventors: Olof Liberg; Béla RATHONYI; Ali Behravan; Martin Van Der Zee
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-09-30
Filing date: 2017-09-27
Publication date: 2018-04-05

Abstract

Embodiments herein relate to a method in a network node (120) serving a cell in a wireless network. The network node (120) sends to a wireless device (110), an indication indicating whether partitioning of random access resources is used or not in the cell.

Description

PARTITIONING OF RANDOM ACCESS RESOURCES

TECHNICAL FIELD Embodiments herein relate to a network node, a wireless device and methods performed therein. Furthermore, a computer program and a computer readable storage medium are also provided herein. In particular, embodiments herein relate to handle or enable communication of one or more wireless devices in a wireless communications network.

BACKGROUND

One goal of the Third Generation Partnership Project (3GPP) long term evolution (LTE) is to improve the Universal Mobile Telecommunications System (UMTS) standard. A 3 GPP LTE radio interface offers high peak data rates, low delays and an increase in spectral efficiencies. The LTE ecosystem supports both frequency division duplex (FDD) and time division duplex (TDD). This enables the operators to use both the paired and unpaired spectrum because LTE has flexibility in bandwidth as it supports 6 bandwidths: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz.

Narrow-band internet of things (NB-IoT) includes a new access system using low complexity and low throughput radio access technology to address the requirements of cellular internet of things. The objective of the Rel-13 work item on NB-IOT is to specify a radio access for cellular internet of things, based on a non-backward-compatible variant of E-UTRA, that addresses improved indoor coverage, support for a massive number of low throughput devices, low delay sensitivity, ultra-low device cost, low device power consumption and (optimized) network architecture.

NB-IoT supports three modes of operation:

1. 'Stand-alone operation' utilizing for example the spectrum currently being used by global system for mobile communication (GSM) EDGE Radio Access Network (GERAN) systems as a replacement of one or more GSM carriers. In principle it operates on any carrier frequency which is neither within the carrier of another system not within the guard band of another system's operating carrier. The other system can be another NB-IOT operation or any other radio access technology (RAT), e.g., LTE.

2. 'Guard band operation' utilizing the unused resource blocks within a LTE carrier's guard-band. The term guard band may also interchangeably be called guard bandwidth. 3. Ίη-band operation' utilizing resource blocks within a normal LTE carrier. The in-band operation may also interchangeably be called in-bandwidth operation.

In NB-IOT the downlink transmission is based on orthogonal frequency division multiplexing (OFDM) with 15 kHz subcarrier spacing for all the scenarios: standalone, guard-band, and in-band. For uplink (UL) transmission, both multi-tone transmissions based on single carrier frequency division multiple access (SC-FDMA), and single tone transmission is supported. A multi-tone transmission is based on SC-FDMA with 15 kHz UL subcarrier spacing. For the single tone transmissions, two numerologies can be configurable by the network: 3.75 kHz and 15 kHz. A cyclic prefix is inserted. This means that the physical waveforms for NB-IoT in downlink and also partly in uplink are similar to legacy LTE.

In the downlink design, NB-IOT supports both master information broadcast and system information broadcast which are carried by different physical channels. For in-band operation, it is possible for NB-IoT user equipment (UE), also referred to as a wireless device, to decode narrowband physical broadcast channel (NPBCH) without knowing the legacy physical resource block (PRB) index. NB-IoT supports both narrowband physical downlink control channel (NPDCCH) and narrowband physical downlink shared channel (NPDSCH). The operation mode of NB-IOT is indicated to the wireless device using the operation mode in the master information block (MIB).

NB-IoT supports a set of narrowband channels, namely the narrowband physical broadcast channel (NPBCH), the narrowband physical downlink control channel (NPDCCH), the narrowband physical downlink shared channel (NPDSCH), the narrowband physical uplink control channel (NPUSCH), and the narrowband physical random access channel (NPRACH). The general design principle of NB-IoT follows that of legacy LTE. Downlink synchronization signal consists of narrowband primary synchronization signal (NPSS) and narrowband secondary synchronization signal (NSSS). Also, cell specific narrowband reference symbols (NRS) are defined for NB-IoT.

To make NB-IoT more suitable for wearables and other applications that require low power and small battery size, Rel-14 NB-IoT has an objective to evaluate and specify a new wireless device power class with lower maximum output power. Currently the maximum power of the new wireless device power class is not decided and the signaling to support the new power class is not specified. It is however assumed that the new wireless device power class will be significantly lower than the currently specified power classes of 20 and 23 dBm, e.g. 14 dBm. In a cellular system, random access (RA) is the process of requesting a connection setup for initial access or to re-establish a radio link. In addition to the usage during initial access, RA is also used when the wireless device has lost the synchronization. Also during a handover process, RA may be used to setup a connection between the wireless device and the new network node.

The random access can be contention-based or contention-free. In a contention- based random-access attempt, the wireless device selects a sequence at random. If the wireless device is requested to perform a contention-free random access, the preamble to use is explicitly signaled to the wireless device by the network node.

The first step in the random access procedure is transmission of a random access preamble. In LTE release 8, there are 64 preamble sequences available per cell. The random access preambles are generated from cyclic shifts of root Zadoff-Chu (ZC) sequences. The length of the Zadoff-Chu sequence depends on the preamble format. For preamble formats 0-3 the length is 839 samples. This length gives the processing gain in the detection of the preamble. The number of orthogonal sequences that can be derived from one root ZC sequence depends on cyclic shift length Δ. In smaller cells, a small cyclic shift can be used, resulting in a larger number of cyclically shifted sequences for each root ZC sequence. A root ZC sequence is generated as: x_u(n) = e ^}^^ ^■ < n < N_zc - \

where u is the index of the sequence and Nzc is the length of the sequence. A property of

ZC sequences is that they are constant amplitude and zero autocorrelation (CAZAC) sequences, which make them ideal for being used as preamble. Also, a discrete Fourier transform (DFT) of a ZC sequence is another ZC sequence, which makes it easy to create them in either the time or frequency domain.

At the network node, the received sequence is correlated with root ZC sequences.

By observing the output of the correlators, it is possible to detect which root ZC sequence and what cyclic shift is used, and what the round-trip time of the channel is. This is due to the ideal auto-correlation properties of cyclic-shifted ZC sequences.

FIGURE 1 illustrates a block diagram of the random access preamble generation and reception in the uplink of LTE. In this figure a root ZC with no cyclic shift is used for the sake of simplicity. The sequence x_u(n) is generated and then transmitted using a SC- FDMA modulator. After the channel, and at the receiver, first the cyclic prefix is removed, and the frequency domain sequence is formed by taking Fast Fourier Transform (FFT) of the sequence. The frequency domain sequence is then element-wise multiplied by X_u ^* , and the result passes through an Inverse Discrete Fourier Transform (IDFT) and a parallel-to- serial transform to get a shifted impulse response.

When a cyclic shifted ZC sequence with a cyclic shift of mA is used, x_u (n + mA modN_zc) , if the basic cyclic shift Δ is larger than the maximum roundtrip time plus the delay spread in a cell, then the sequences are orthogonal at the receiver. In this case the detected signal will be the channel impulse response at h(n + mA modN_zc) .

For NB-IoT a random access preamble corresponds to a random access symbol group that is constructed of 5 identical symbols and a cyclic prefix, see TS 36.21 1, section 10.1.6.1, v 13.0.0. Each symbol corresponds to an unmodulated sinus wave of length 8192 Ts, where Ts equals 1/(15000x2048) sec, transmitted over a 3.75 kHz channel.

The NB-IoT minimum system bandwidth of 180 kHz is dividable in totally 48 sub- carriers, or tones. FIGURE 2 illustrates a random access symbol group of length 1.4 or 1.6 ms. For a single NPRACH transmission the preamble of FIGURE 2 is hopping four times across at most seven sub-carriers. A preamble is uniquely defined by the first sub-carrier in the hopping pattern, i.e. the starting sub-carrier. In total 48 orthogonal preambles can be defined, one for each available starting sub-carrier.

FIGURE 3 illustrates a random access frequency hopping symbol group configured with a 1.6 ms long symbol group. The network node NPRACH resource illustrated in FIGURE 3 is intended for wireless devices in good radio conditions, where the random access frequency hopping symbol group is sent a single time. A network node may configure two additional NPRACH resources to be used by wireless devices in extended and extreme coverage. Each NPRACH resource is associated with a set of repetitions of the random access frequency hopping symbol group. The number of repetitions is increasing with the coverage intended to be supported by the NPRACH resource. The wireless device measures the downlink received power and makes based on this, and a set of broadcasted signal level thresholds a selection of the NPRACH resource to use for its system access, i.e. the number of times the random access frequency hopping symbol group should be repeated.

At most 128 repetitions of the random access frequency hopping symbol group illustrated in FIGURE 3 is supported. In case of repetitions a pseudo random frequency hop is performed between two frequency hopping symbol groups. The signal generated across a set of repetitions will at most hop across 12 sub-carriers.

When the network node receives a random access attempt in one of the NB-IoT NPRACH resources it may use the number of repetitions used by the wireless device and the received signal level as indications of the coverage level of the wireless device. For B-IoT in Release 13 all wireless devices use an output power of 20 or 23 dBm. This knowledge in combination with the received signal level allows the network node to calculate the coupling loss (CL) between the network node and the wireless device as: coupling loss = wireless device output power - received PRACH signal power at network node.

The knowledge of the CL and the repetition level may later be used by the network node when deciding the radio resources to use when scheduling downlink and uplink radio resources to the wireless device. Radio resources may here refer to the power, modulation and coding scheme as well as the assigned number of sub-carriers and repetitions.

The NPRACH configuration information discussed herein is transmitted in e.g. a RadioResouceConfigCommonSIB-NB-rl3 information element (IE) that is contained in SystemInformationBlockType2-NB (SIB2-NB). Updates of the SIB2-NB follows the system information modification boundaries which in the case of NB-IoT means that the NPRACH configuration information can be updated at most every 40.96 sec, see modificationPeriodCoeff field in TS 36.331 v.13.0.0.

A particular problem associated with the introduction of a wireless device with a lower power class is that the network node loses its knowledge of the output power of the wireless device. If the network node does not know the maximum transmit power of the wireless device, it cannot perform a coupling loss (CL) calculation with accuracy. In Release 13 an ambiguity exists because both 20 and 23 dBm wireless devices are supported. Introduction of a new power class significantly lower than 20 dBm further increases the ambiguity and thus CL estimation becomes unreliable. As a consequence, the network node will need to always make the conservative assumption that a 23 dBm wireless device accessed the network node and estimate the CL as: coupling loss = 23 dBm - received NPRACH signal power at eNB.

When a Release 14 wireless device of low output power accesses the network node, the network node may over-estimate the coupling loss between the wireless device and the network node. This is a problem at the initial access where the wireless device first sends a random access preamble to the network node. As a result of this, the network node assigns too much radio resources for the random access response and subsequent messages sent back to the wireless device until the network node learns the wireless device power class via established wireless device capability transfer procedures. This waste of radio resources increases the load and the interference levels in the wireless network. SUMMARY

An object of embodiments herein is to provide a mechanism that enables an efficient use of radio resources in a wireless network.

According to an aspect the object is achieved by providing a method performed by a network node serving a cell in a wireless network. The network node sends to a wireless device, an indication indicating whether partitioning of random access resources is used or not in the cell.

According to another aspect the object is achieved by providing a method performed by a wireless device served in a cell of a network node in a wireless network. The wireless device obtains from the network node, an indication indicating whether partitioning of random access resources is used in the cell or not.

It is furthermore provided herein a computer program comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry out any of the methods above, as performed by the network node or the wireless device. It is additionally provided herein a computer-readable storage medium, having stored thereon a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of the methods above, as performed by the network node or the wireless device.

According to yet another aspect the object is achieved by providing a network node configured to serve a cell in a wireless network. The network node is configured to send to a wireless device, an indication indicating whether partitioning of random access resources is used or not in the cell.

According to still another aspect the object is achieved by providing a wireless device configured for a wireless network, which wireless network comprises a network node serving a cell in the wireless network. The wireless device is configured to obtain from the network node, an indication indicating whether partitioning of random access resources is used in the cell or not.

Particular embodiments alleviate the disadvantages described above. Particular embodiments include methods to dynamically inform wireless devices in a cell about which e.g. random access preambles should be used for each wireless device. Particular embodiments define a new information element (IE) determining the random access resource partitioning that can be dynamically updated and that a wireless device reads before performing a system access. The new IE may e.g. be signaled via the master information block (MIB), a system information block (SIB), via a synchronization channel, or via a common control channel, etc.

According to some embodiments herein, a method performed by a network node is provided, wherein the network node may partition random access resources for the cell into one or more partitions. The network node further transmits, to the wireless device, e.g. an information element indicating the partitioning of the random access resources which information element the wireless device may read before performing a system access. The network node further receives a random access message from the wireless device using a random access resource from one of the partitions.

A particular advantage of some embodiments is that dynamic random access resource partitioning enables the available random access resources to be used efficiently and may avoid overload scenarios leading to a congestion of e.g. the Narrowband Physical Random Access Channel (NPRACH). Embodiments herein also enable the network node to identify wireless devices of e.g. a certain output power based on random access resources used and may enable a more optimal assigning of radio resources leading to a more efficient use of radio resources in the wireless network.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments and their features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 illustrates a block diagram of the random access preamble generation and reception in the uplink of LTE;

FIGURE 2 illustrates a random access symbol group of length 1.4 or 1.6 ms;

FIGURE 3 illustrates a random access frequency hopping symbol group configured with a 1.6 ms long symbol group;

FIGURE 4A is a block diagram illustrating an example wireless network, according to a particular embodiment;

FIGURE 4B is a flow diagram of an example method performed by a network node, according to some embodiments;

FIGURE 4C is a flow diagram of an example method performed by a wireless device, according to some embodiments;

FIGURE 4D is a combined flowchart and signaling scheme of an example method in a wireless network, according to some embodiments; FIGURE 5 illustrates random access attempts and the available random access opportunities in (a) and divided random access opportunities in (b), according to some embodiments;

FIGURE 6 illustrates applying preamble resource partitioning by using a single bit information element, according to some embodiments;

FIGURE 7 illustrates a single parameter m representing the partitioning of preamble sequences, according to a particular embodiment;

FIGURE 8 is a flow diagram of an example method in a wireless device, according to some embodiments;

FIGURE 9 is a flow diagram of an example method in a network node, according to some embodiments;

FIGURE 1 OA is a block diagram illustrating an example embodiment of a wireless device;

FIGURE 10B is a block diagram illustrating example components of a wireless device;

FIGURE 11A is a block diagram illustrating an example embodiment of a network node; and

FIGURE 1 IB is a block diagram illustrating example components of a network node.

DETAILED DESCRIPTION

With the introduction of additional low UE power classes, the network node may no longer make assumptions about a UEs output power, which means the network node cannot perform coupling loss (CL) calculation with accuracy. One solution to this problem may be to reserve a set of random access preambles, such as NPRACH resources, dedicated for wireless devices of lower output power. This early indication of the output power of the wireless device will allow the network node to correctly calculate the CL. Thus, the available random access sub-carriers are split, or partitioned, between wireless devices of high output power and wireless devices of low output power. To optimize this split of the configured sub-carriers an operator will need to record statistics of the level of high and low power wireless devices. This results, however, in a configuration that is only optimized over a long time line. At any given moment, there is no guarantee that the partitions are optimal, which may lead to a sudden overload scenario where the number of wireless devices of a certain power class accessing a network node exceeds the available sub-carriers dedicated to the same power class. It is also likely that the partition of the random access resources would be placed in the RadioResouceConfigCommonSIB-NB-rl3 IE contained in SIB2- B. The shortest allowed modification period of this information, i.e. 40.92 sec, is not sufficiently fast to allow for a reconfiguration of the partitions to solve the overload scenario referred to above.

According to embodiments herein a network node informs one or more wireless devices whether partitioning is used or not in a cell of the network node. Thus, the wireless device is informed and may use random access resources indicating capacity of the wireless device and the network node may assign radio resources more efficiently.

Particular embodiments include methods to dynamically inform wireless devices in a cell about which random access preambles should be used for each power class. Particular embodiments define a new information element (IE) determining the random access resource partitioning that can be dynamically updated and that a UE reads before performing a system access.

The description herein sets forth numerous specific details. It is understood, however, that embodiments may be practiced without these specific details. In other instances, well- known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.

References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

Some embodiments include partitioning random access resources, such as NPRACH resources, and adapting the partition size to the number of wireless devices in each power class. Particular embodiments are described with reference to FIGURES 4A-1 1B of the drawings, like numerals being used for like and corresponding parts of the various drawings. LTE is used throughout this disclosure as an example cellular system, but the ideas presented herein may apply to other wireless communication systems as well. FIGURE 4A is a block diagram illustrating an example wireless network, according to a particular embodiment. Wireless network 100 includes one or more wireless devices 1 10 (such as mobile phones, smart phones, laptop computers, tablet computers, MTC devices, or any other devices that can provide wireless communication) and a plurality of network nodes 120 (such as base stations or eNodeBs). Network node 120 serves coverage area 115 (also referred to as cell 115).

In general, wireless devices 110 that are within coverage of network node 120 (e.g., within cell 115 served by network node 120) communicate with network node 120 by transmitting and receiving wireless signals 130. For example, wireless devices 110 and network node 120 may communicate wireless signals 130 containing voice traffic, data traffic, and/or control signals. A network node 120 communicating voice traffic, data traffic, and/or control signals to wireless device 110 may be referred to as a serving network node 120 for the wireless device 110.

In some embodiments, wireless device 110 may be referred to by the non-limiting term "UE." A UE may include any type of wireless device capable of communicating with a network node or another UE over radio signals. The UE may comprise radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), a sensor equipped with UE, iPAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), etc.

In some embodiments, network node 120 may include any type of network node such as a network node e.g. base station, radio base station, base transceiver station, base station controller, network controller, evolved Node B (eNB), Node B, multi-RAT base station, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH), or a core network node (e.g., MME, SON node, a coordinating node, etc.), or even an external node (e.g., 3rd party node, a node external to the current network), etc.

Wireless signals 130 may include both downlink transmissions (from network node 120 to wireless devices 110) and uplink transmissions (from wireless devices 110 to network node 120). Before sending an uplink transmission, wireless device 110 may perform a random access procedure to access cell 115.

According to embodiments herein the network node 120 sends to the wireless device 110, an indication indicating whether partitioning of random access resources is used or not in the cell. Wireless devices 110 may belong to different output power classes. When performing the random access procedure, wireless device 110 may, in some embodiments, use different random access resources depending on its output power class. Network node 120 may signal to wireless device 110 which random access resources to use for a particular power class and thereby indicate that partitioning is used.

Each network node 120 may have a single transmitter or multiple transmitters for transmitting wireless signals 130 to wireless devices 110. In some embodiments, network node 120 may comprise a multi-input multi-output (MEVIO) system. Similarly, each wireless device 110 may have a single receiver or multiple receivers for receiving signals 130 from network nodes 120.

In wireless network 100, each network node 120 may use any suitable radio access technology, such as long term evolution (LTE), LTE-Advanced, NR, UMTS, HSPA, GSM, cdma2000, WiMax, WiFi, and/or other suitable radio access technology. Wireless network 100 may include any suitable combination of one or more radio access technologies. For purposes of example, various embodiments may be described within the context of certain radio access technologies. However, the scope of the disclosure is not limited to the examples and other embodiments could use different radio access technologies.

As described above, embodiments of a wireless network may include one or more wireless devices and one or more different types of network nodes capable of communicating with the wireless devices. The wireless network may also include any additional elements suitable to support communication between wireless devices or between a wireless device and another communication device (such as a landline telephone). A wireless device may include any suitable combination of hardware and/or software. For example, in particular embodiments, a wireless device, such as wireless device 110, may include the components described below with respect to FIGURE 10A. Similarly, a network node may include any suitable combination of hardware and/or software. For example, in particular embodiments, a network node, such as network node 120, may include the components described below with respect to FIGURE 11 A.

Particular embodiments include partitioning random access resources and adapting the partition size to the number of wireless devices in each power class. In some embodiments, the available PRACH sequences are divided into several groups corresponding to the number of the wireless devices in each power class. Although particular embodiments are described in NB-IoT context, in general the embodiments may be applied to LTE or any other cellular system that uses a random access procedure. FIGURE 4B is a schematic flowchart depicting a method performed by the network node 120 serving the cell in the wireless network according to embodiments herein. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some, but not necessarily all, embodiments are marked with dashed boxes.

Action 401. The network node 120 may partition random access resources for the cell into one or more partitions. The network node 120 may partition the random access resources based on a frequency of access requests on certain partitions. The partitioned random access resources may comprise frequencies, time slots, preambles or similar. The network node 12 may take how often access requests are performed in certain partitions and adjust more random access resources to certain frequencies or time slots. The network node 120 may partition random access resources by adapting a size of each partition based on at least one of: prioritizing certain applications, improving cell throughput, and reducing access delay.

Action 402. The network node 120 sends to the wireless device 110, the indication indicating whether partitioning of random access resources is used or not in the cell. The indication may be a flag and/or preamble sequences to use. For example, the network node 120 may send the indication indicating that partitioning of random access resources is used in the cell, such as the flag or the preambles of one or more partitions. The network node may send the indication in at least one of: a MIB, a SIB, or a common control channel. The indication indicating that partitioning of random access resources is used in the cell comprises information about one or more partitions of random access resources for the cell, such as how the random access resources are partitioned, which random access resources to use etc. The indication indicating that partitioning of random access resources is used in the cell comprises a range of preamble sequences for use by a particular power class of wireless devices.

Action 403. The network node 120 may receive a random access message from the wireless device 110 using a random access resource of the partitioned random access resources.

Action 404. The network node 120 may merge the one or more partitions into a full set of random access resources. The network node 120 may then in action 402 send the indication indicating that partitioning is not used in the cell.

FIGURE 4C is a schematic flowchart depicting a method performed by the wireless device 110 served in the cell of the network node 120 in the wireless network according to embodiments herein. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some, but not necessarily all, embodiments are marked with dashed boxes.

Action 411. The wireless device obtains, e.g. receives, from the network node 120, the indication indicating whether partitioning of random access resources is used in the cell or not. The wireless device 110 may obtain the indication indicating that partitioning of random access resources is used in the cell. The indication indicating that partitioning of random access resources is used may comprise information about one or more partitions of random access resources for the cell. The indication indicating that partitioning of random access resources is used may comprise the range of preamble sequences for use by a particular power class of wireless devices. The wireless device 110 may obtain the indication indicating whether partitioning of random access resources is used or not by receiving the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

Action 412. The wireless device 110 may select one partition of partitioned random access resources based on the output power class of the wireless device.

Action 413. The wireless device 110 may select the random access resource from the selected one partition.

Action 414. The wireless device 110 may transmit the random access message to the network node using a random access resource out of partitioned random access resources.

Action 415. The wireless device 110 may, when the obtained indication indicates that partitioning of random access resources is not used in the cell, select a random access resource from a full set of random access resources, and the wireless device may transmit to the network node, the random access message to the network node using the selected random access resource out of the full set of random access resources

FIGURE 4D is a schematic combined flowchart and signaling scheme according to some embodiments herein.

Action 421. The network node 120, such as a e B, transmits the indication indicating whether partitioning of random access resources is used or not in the cell. E.g. the network node 120 transmits a flag or preamble sequences of a partition indicating that partitioning of random access resources is used.

Action 422. The wireless device 110 may then select random access resource to use when performing a random access procedure. E.g. the wireless device 110 may select a preamble out the preambles of a partition for wireless devices of a certain output power e.g. below a output power threshold or a power class.

Action 423. The wireless device 110 may then transmit the random access request using the selected random access resource, e.g. preamble.

Action 424. The network node 120, receiving the random access request, may then assign radio resources based on the used random access resource of the random access request. Additionally or alternatively, the network node 120 may adapt size of the different partitions based on the used random access resource of the random access request.

FIGURE 5 illustrates random access attempts and the available random access opportunities in (a) and divided random access opportunities in (b), according to some embodiments. In FIGURE 5, λ is the number of random-access attempts per second and per cell, and L is the number of random-access opportunities per second per cell. The random access opportunities (L) are divided corresponding to the number of random access attempts from different power classes (λι and λ₂).

The network node 120 may update the size of random access resources such as preamble resources in each group in different ways. In one embodiment, the update may be based on a frequency of access requests, i.e. how often, on certain partitions of PRACH, where the network node 120 logs the number of random access attempts in each class and applies the partitioning over a certain time interval. Alternatively, the update of the preamble partitions may be done based on the access that was granted to wireless devices of the power classes. In some embodiments, the network node 120 may adapt the size of each partition to meet certain requirements such as prioritizing certain applications, improving cell throughput, reducing the access delay, etc.

Based on the time interval for which the adaptation applies, the assignment may be adapted to be more dynamic or less dynamic. An advantage of dynamic adaptation is to avoid overload scenarios.

Particular embodiments may broadcast the information related to preamble resource partitioning. For example, in particular embodiments the partitioning of random access resources for PRACH preamble is broadcasted in the cell by different downlink channels and/or signals that are broadcasted in the cell and are common for all wireless devices.

In particular embodiments, the partitioning information may be carried by a system information channel, e.g. SIB2 that contains random access related parameters, MIB, or a common control channel (e.g., a channel carrying paging messages). In the MIB, SIB or paging message, particular embodiments may define one or more new information elements for the signaling of the PRACH partitioning. The wireless device 110 may read at least one of the new information elements ( Es) before performing a system access to understand if the partitioning has been updated.

A particular embodiment of informing wireless devices about the partitioning in a cell defines two states for preamble resource partitioning in the cell. Either a pre-determined partitioning is used in the cell, or no preamble partitioning is used in the cell.

For NB-IoT the RA resources such as RA preambles are defined as a frequency hopping sinusoidal waveforms. Figure 3 above illustrates this. A preamble is defined by its starting sub-carrier (= frequency) and its frequency hopping pattern. The NB-IoT specification supports partitioning by means of dividing the starting sub-carriers into two sets. The second set is used to indicate that the wireless device supports multi-tone transmission in Msg3. So if a wireless device accesses the radio network node using a preamble from the second set then the radio network node can schedule that UE using multitone transmission in Msg3, this is shown in Figure 5. The set Li corresponds to the first set of starting subcarriers and L₂ corresponds to the second set of starting subcarriers. For NB-IoT a random access opportunity corresponds to the selection of a starting subcarrier and subsequent transmission according to the generated frequency hopping pattern.

FIGURE 6 illustrates applying RA resource partitioning by using a single bit information element, according to some embodiments. A single bit information element is used where one state (which may be the default state) represents that a partitioning of the random access resources is applied in the cell. The second state represents no partitioning is applied in the cell, where it can override the default state when broadcasted in e.g. the MIB. The wireless device 110 may acquire the status of the single bit IE before accessing the cell.

In some embodiments, the network node 120 configures a multitude of NPRACH resources. For each of the NPRACH resources a flag (for example a single bit) is broadcasted, in e.g. the MIB, to inform the wireless devices if partitioning is used or not.

In some embodiments, the partitioning information may include a range of preamble sequences that can be used for random access by different power classes in a cell. FIGURE 7 illustrates a single parameter m representing the partitioning of preamble sequences, according to a particular embodiment.

In the example of FIGURE 7, an available set of resources LI-LM is divided into two groups. Li-Lm are reserved for one power class while the rest of preambles L_m+i-LM are reserved for a second power class. In this case the network node 120 may only broadcast the value m (or M-(m+l)) in an information element that corresponds to the partitioning the preamble sequences. The available set of resources LM may correspond to the full set of preambles available in a NPRACH resource, or it may correspond to a fraction thereof, e.g. a since earlier defined partition. The wireless device 1 10 may acquire the status of the value m before accessing the cell.

In some embodiments, the network node 120 configures a multitude of NPRACH resources. For each of the NPRACH resources a separate instance of the value m is broadcasted, in e.g. the MIB, to inform the wireless devices of the used partitioning.

In some embodiments, the information of the partitioning may be placed in a separate

SIB (denoted SIBxy-NB) with the same/similar rules as the existing SIB14-NB, i.e. a change can occur at any point in time, a flag in the MIB is indicating if the wireless device 110 should read SIBxy-NB and change to any of the parameters does not impact the systemlnfoValueTag in the MasterlnformationBlock-NB or the systemlnfoValueTagSI in SystemlnformationBlockTypel-NB. The new SIBxy-NB contains information of the dynamic partitioning part, e.g. number of start sub-carriers (or preamble sequences) reserved for a certain power class or a simple on/off flag per NPRACH resource.

In particular embodiments, the NPRACH configuration in SIB2-NB includes the semi- static partitioning information that applies when the flag in the MIB is not set (e.g., a value m or a fraction value as described above). The SIBxy-NB may either include delta information and/or absolute information of the changes compared to the semi-static SIB2-NB NPRACH configuration. There are many possibilities of what dynamic partitioning information that could be included in the SIBxy-NB and below a few examples are listed:

• A delta value for the number of start sub-carriers, where a start sub-carrier uniquely defines a distinct preamble, that are allowed to be used by the wireless device, i.e. a positive or negative value X. The normal power class wireless devices use the partition [Li, L_m+x] and low power class wireless devices use [L_m+i+x, LM]. The value of X may be included in SIBxy-NB.

• Information that all start sub-carriers from a NPRACH resource are allowed to be used by low power class wireless devices. In some embodiments, only a sub-set such as the

Y first or Y last (Y>0) are allowed to be used, i.e. [Li, Ly] and [L_m+i-y, L_m] respectively. The value of Y may be included in SIBxy-NB.

• Information that all wireless devices regardless of power class are allowed to use the reserved start sub-carriers for low power class UEs, i.e. [L_m+i, LM] but low power class wireless devices are only allowed to access using the partition [L_m+i, LM]. In some embodiments, only a sub-set such as the Z first or Z last (Z>0) may be used, i.e.

[Lm+i, Lm+z] and [LM+I-Z, LM] respectively. The value of Z may be included in SIBxy- B.

In some embodiments, the information of the dynamic partitioning may be included in the existing SIB14- B containing Access class Barring information. This is similar to some previously described embodiments, but no new flag is included in the MIB and no new SIBxy- B is introduced. The same information is included as new parameters in the SIB 14- B.

FIGURE 8 is a flow diagram of an example method in a wireless device, according to some embodiments. In particular embodiments, one or more steps of method 800 may be performed by components of wireless network 100 described with reference to FIGURES 4A- 11B.

Method 800 begins at step 812, where the wireless device 110 obtains information about one or more partitions of random access resources for a cell. For example, in particular embodiments wireless device 110 may obtain information about one or more partitions of random access resources for cell 115 using any of embodiments described herein.

At step 814, the wireless device 110 selects one partition based on an output power class of the wireless device. For example, wireless device 110 may comprise a low power device and wireless device 110 may select one partition partitioned for low power devices according to any of the embodiments described herein.

At step 816, the wireless device selects a random access resource from the selected one partition. For example, wireless device 110 may select a random access resource from the partition selected in the previous step according to any of the embodiments described herein.

At step 818, the wireless device performs a random access procedure using the selected random access resource. For example, wireless device 110 may perform a random access procedure using the random access resource selected in the previous step according to any of the embodiments described herein.

Modifications, additions, or omissions may be made to method 800 illustrated in

FIGURE 8. Additionally, one or more steps in method 800 may be performed in parallel or in any suitable order.

FIGURE 9 is a flow diagram of an example method in a network node, according to some embodiments. In particular embodiments, one or more steps of method 900 may be performed by components of wireless network 100 described with reference to FIGURES 4A- 11B.

Method 900 begins at step 912, where the network node 120 partitions random access resources for a cell into one or more partitions. For example, in particular embodiments network node 120 may partition random access resources for cell 115 into one or more partitions.

At step 914, the network node 120 sends an indication of the partitioning of random access resources to a wireless device. For example, in particular embodiments network node 120 may send an indication of the partitioning of random access resources to wireless device 110 according to any of the embodiments described herein.

At step 916, the network node 120 receives a random access message from the wireless device using a random access resource determined based on an output power of the wireless device. For example, in particular embodiments network node 120 may receive a random access message from wireless device 110 using a random access resource determined based on the wireless device 110 being a low power wireless device according to any of the embodiments described herein.

Modifications, additions, or omissions may be made to method 900 illustrated in FIGURE 9. Additionally, one or more steps in method 900 may be performed in parallel or in any suitable order.

FIGURE 10A is a block diagram illustrating an example embodiment of the wireless device 110. The wireless device 110 is an example of the wireless devices 110 illustrated in FIGURE 4A. Particular examples include a mobile phone, a smart phone, a PDA (Personal Digital Assistant), a portable computer (e.g., laptop, tablet), a sensor, a modem, a machine type (MTC) device / machine to machine (M2M) device, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, a device-to-device capable device, a B- IoT device, or any other device that can provide wireless communication. The wireless device includes transceiver 1010, processor 1020, and memory 1030. In some embodiments, transceiver 1010 facilitates transmitting wireless signals to and receiving wireless signals from network node 120 (e.g., via an antenna), processor 1020 executes instructions to provide some or all of the functionality described herein as provided by the wireless device, and memory 1030 stores the instructions executed by processor 1020.

Processor 1020 includes any suitable combination of hardware and software implemented in one or more integrated circuits or modules to execute instructions and manipulate data to perform some or all of the described functions of the wireless device. In some embodiments, processor 1020 may include, for example, one or more computers, one more programmable logic devices, one or more central processing units (CPUs), one or more microprocessors, one or more applications, and/or other logic, and/or any suitable combination of the preceding. Processor 1020 may include analog and/or digital circuitry configured to perform some or all of the described functions of wireless device 110. For example, processor 1020 may include resistors, capacitors, inductors, transistors, diodes, and/or any other suitable circuit components.

Memory 1030 is generally operable to store computer executable code and data. Examples of memory 1030 include computer memory (e.g., Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (e.g., a hard disk), removable storage media (e.g., a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or or any other volatile or non-volatile, non-transitory computer-readable and/or computer-executable memory devices that store information.

In particular embodiments, processor 1020 in communication with transceiver 1010 communicates wireless signals with network node 120 or other wireless devices 110. In particular embodiments, the wireless signals may include random access signals. The random access signals may be partitioned according to any of the embodiments described herein. Other embodiments of the wireless device may include additional components (beyond those shown in FIGURE 10A) responsible for providing certain aspects of the wireless device's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solution described above).

FIGURE 10B is a block diagram illustrating example components of the wireless device 110 configured for the wireless network, which wireless network comprises the network node serving the cell in the wireless network. The components may include obtaining module 1050, selecting module 1052, and random access module 1056.

The wireless device 110, the processor 1020, and/or the obtaining module 1050, e.g. a receiver or transceiver, is configured to obtain from the network node, the indication indicating whether partitioning of random access resources is used in the cell or not. The wireless device 110, the processor 1020, and/or the obtaining module 1050 may be configured to obtain the indication indicating that partitioning of random access resources is used in the cell. The wireless device 110, the processor 1020, and/or the random access module 1056, e.g. a transmitter or transceiver, may be configured to transmit the random access message to the network node using the random access resource out of partitioned random access resources. The indication indicating that partitioning of random access resources is used may comprise information about one or more partitions of random access resources for the cell. The indication indicating that partitioning of random access resources is used may comprise the range of preamble sequences for use by a particular power class of wireless devices.

The wireless device 110, the processor 1020, and/or the selecting module 1052 may be configured to select one partition of partitioned random access resources based on an output power class of the wireless device. The wireless device 110, the processor 1020, and/or the selecting module 1052 may further be configured to select the random access resource from the selected one partition.

The wireless device 110, the processor 1020, and/or the obtaining module 1050 may be configured to receive the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

The wireless device 110, the processor 1020, and/or the obtaining module 1050 may be configured to obtain the indication that partitioning of random access resources is not used in the cell. The wireless device 110, the processor 1020, and/or the selecting module 1052 may then be configured to select a random access resource from a full set of random access resources. The wireless device 110, the processor 1020, and/or the random access module 1056, e.g. a transmitter or transceiver, may then be configured to transmit to the network node, the random access message to the network node using the selected random access resource out of the full set of random access resources.

Obtaining module 1050 may perform the obtaining functions of wireless device 110.

For example, obtaining module 1050 may obtain information about one or more partitions of random access resources for a cell according to any of the embodiments described herein. In certain embodiments, obtaining module 1050 may include or be included in processor 1020. In particular embodiments, obtaining module 550 may communicate with selecting module 1052 and random access module 1056.

Selecting module 1052 may perform the selecting functions of wireless device 110. For example, selecting module 1052 may select one partition based on an output power class of the wireless device and select a random access resource from the selected one partition according to any of the embodiments described herein. In certain embodiments, selecting module 1052 may include or be included in processor 1020. In particular embodiments, selecting module 1052 may communicate with obtaining module 1050 and random access module 1056.

Random access module 1056 may perform the random access functions of wireless device 110. For example, random access module 1056 may perform a random access procedure using the selected random access resource. In certain embodiments, random access module 1056 may include or be included in processor 1020. In particular embodiments, random access module 1056 may communicate with obtaining module 1050 and selecting module 1052.

FIGURE 11A is a block diagram illustrating an example embodiment of the network node 120. Network node 120 can be an eNodeB, a nodeB, a base station, a wireless access point (e.g., a Wi-Fi access point), a low power node, a base transceiver station (BTS), a transmission point or node, a remote RF unit (RRU), a remote radio head (RRH), or other radio access node. Network node 120 includes at least one transceiver 1110, at least one processor 1120, at least one memory 1130, and at least one network interface 1140. Transceiver 1110 facilitates transmitting wireless signals to and receiving wireless signals from a wireless device, such as wireless devices 110 (e.g., via an antenna); processor 1120 executes instructions to provide some or all of the functionality described above as being provided by a network node 120; memory 1130 stores the instructions executed by processor 1120; and network interface 1140 communicates signals to backend network components, such as a gateway, switch, router, Internet, Public Switched Telephone Network (PSTN), controller, and/or other network nodes. Processor 1120 and memory 1130 can be of the same types as described with respect to processor 1020 and memory 1030 of FIGURE 10A above.

In some embodiments, network interface 1140 is communicatively coupled to processor 1120 and refers to any suitable device operable to receive input for network node 120, send output from network node 120, perform suitable processing of the input or output or both, communicate to other devices, or any combination of the preceding. Network interface 1140 includes appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network. In particular embodiments, processor 1120 in communication with transceiver 1110 partitions random access resources and sends an indication of the partitioning to wireless device 110.

Other embodiments of network node 120 include additional components (beyond those shown in FIGURE 11 A) responsible for providing certain aspects of the network node's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solution described above). The various different types of network nodes may include components having the same physical hardware but configured (e.g., via programming) to support different radio access technologies, or may represent partly or entirely different physical components. FIGURE 11B is a block diagram illustrating example components of the network node 120 serving the cell in the wireless network. The components may include partitioning module 1150, sending module 1152, and receiving module 1154.

The network node 120, the processor 1120, and/or the sending module 1152, e.g. a transmitter or transceiver, is configured to send to the wireless device 110, the indication indicating whether partitioning of random access resources is used or not in the cell.

The network node 120, the processor 1120, and/or the partitioning module 1150, may be configured to partition random access resources for the cell into one or more partitions. The network node 120, the processor 1120, and/or the sending module 1152, e.g. a transmitter or transceiver, may be configured to send to the wireless device 110, the indication indicating that partitioning of random access resources is used in the cell. The network node 120, the processor 1120, and/or the receiving module 1154, e.g. a receiver or transceiver, may then be configured to receive the random access message from the wireless device 110 using the random access resource of the partitioned random access resources. The indication indicating that partitioning of random access resources is used in the cell may comprise information about one or more partitions of random access resources for the cell. The indication indicating that partitioning of random access resources is used in the cell may comprise the range of preamble sequences for use by a particular power class of wireless devices.

The network node 120, the processor 1120, and/or the partitioning module 1150, may be configured to partition the random access resources based on a frequency of access requests on certain partitions. The network node 120, the processor 1120, and/or the partitioning module 1150, may be configured to adapt the size of each partition of random access resources based on at least one of: prioritizing certain applications, improving cell throughput, and reducing access delay.

The network node 120, the processor 1120, and/or the sending module 1152, e.g. a transmitter or transceiver, may be configured to send the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

The network node 120, the processor 1120, and/or the partitioning module 1150, may be configured to merge the one or more partitions into a full set of random access resources; and then the network node 120, the processor 1120, and/or the sending module 1152 may be configured to send the indication indicating that partitioning is not used in the cell.

Partitioning module 1150 may perform the partitioning functions of network node 120. For example, partitioning module 1 150 may partition random access resources for a cell into one or more partitions according to any of the embodiments described herein. In certain embodiments, partitioning module 1150 may include or be included in processor 1120. In particular embodiments, partitioning module 1150 may communicate with sending module 1152 and receiving module 1154.

Sending module 1152 may perform the sending functions of network node 120. For example, sending module 1152 may send an indication of the partitioning of random access resources to wireless device 110 according to any of the embodiments described herein. In certain embodiments, sending module 1152 may include or be included in processor 1120. In particular embodiments, sending module 1152 may communicate with partitioning module 1150 and receiving module 1154.

Receiving module 1154 may perform the receiving functions of network node 120. For example, receiving module 1154 may receive a random access message from wireless device 110 using a random access resource determined based on an output power of wireless device 110 according to any of the embodiments described herein. In certain embodiments, receiving module 1154 may include or be included in processor 1120. In particular embodiments, receiving module 1154 may communicate with partitioning module 1150 and sending module 1152.

Some embodiments of the disclosure may provide one or more technical advantages. Some embodiments may benefit from some, none, or all of these advantages. Other technical advantages may be readily ascertained by one of ordinary skill in the art. A technical advantage of some embodiments is that dynamic NPRACH resource partitioning enables the available NPRACH resources to be used efficiently and may avoid overload scenarios leading to a congestion of the NPRACH.

Abbreviations:

3 GPP 3rd Generation Partnership Project

BLER Block Error Rate

DL Downlink

eMTC enhanced MTC

eNB Evolved Node B

eNodeB Evolved Node B

E-UTRA Enhanced UTRA

FDD Frequency Division Duplex

IoT Internet of Things

LTE Long-Term Evolution MIB Master Information Block

MTC Machine Type Communication

NB-IoT Narrow-Band Internet of Things

NPRACH NB-IoT Physical Random Access Channel

PSS NB-IoT Primary Synchronization Signal

NSSS NB-IoT Secondary Synchronization Signal

R New Radio

OFDM Orthogonal Frequency

PDCCH Physical Downlink Control Channel

RAT Radio Access Technology

RRC Radio Resource Control

SC-FDMA Single Carrier Frequency Domain Multiple Access

SIB System Information Block

TDD Time Division Duplex

UE User Equipment

UL Uplink

UMTS Universal Mobile Telecommunications System

UTRA UMTS Terrestrial Radio Access

The following list provides non-limiting examples of disclosed embodiments. The examples are merely intended to illustrate how certain aspects of the proposed solutions could be implemented, however, the proposed solutions could also be implemented in other suitable manners. Examples when the wireless device 110 selects partitions based on output power include:

Example 1 : A method in a wireless device, the method comprising:

obtaining information about one or more partitions of random access resources for a cell;

selecting one partition of the one or more partitions based on an output power class of the wireless device;

selecting a random access resource from the selected one partition; and

performing a random access procedure using the selected random access resource.

The method of example 1, wherein obtaining information about the one or more partitions of random access resources for the cell comprises obtaining information from at least one of a master information block (MIB), a system information block (SIB), or a common control channel.

The method of example 1, wherein obtaining information about the one or more partitions of random access resources for the cell comprises obtaining an indication of whether partitioning is used in the cell.

The method of example 1, wherein the information about the one or more partitions of random access resources for the cell comprises a range of preamble sequences for use by a particular power class.

A wireless device comprising a processor and a memory, the processor operable to perform any of the steps of examples 1-4:

Network node examples:

Example 1 : A method in a network node, the method comprising:

partitioning random access resources for a cell into one or more partitions;

sending an indication of the partitioning of random access resources to a wireless device; and

receiving a random access message from the wireless device using a random access resource determined based on an output power of the wireless device.

The method of example 1, wherein sending an indication of the partitioning of random access resources comprises sending information in at least one of a master information block (MIB), a system information block (SIB), or a common control channel. The method of example 1, wherein the indication of the partitioning of random access resources comprises an indication of whether partitioning is used in the cell.

The method of example 1, wherein the indication of the partitioning of random access resources comprises a range of preamble sequences for use by a particular power class.

The method of example 1, wherein partitioning random access resources comprises partitioning the random access resources based on a frequency of access requests on certain partitions.

The method of example 1, wherein partitioning random access resources comprises adapting a size of each partition based on at least one of prioritizing certain applications, improving cell throughput, and reducing access delay.

A network node comprising a processor and a memory, the processor operable to perform any of the steps of examples 1-6.

According to some embodiments, a method in a wireless device comprises: obtaining information about one or more partitions of random access resources for a cell; selecting one partition of the one or more partitions based on an output power class of the wireless device; selecting a random access resource from the selected one partition; and performing a random access procedure using the selected random access resource.

According to some embodiments, a method in a network node comprises: partitioning random access resources for a cell into one or more partitions; sending an indication of the partitioning of random access resources to a wireless device; and receiving a random access message from the wireless device using a random access resource determined based on an output power of the wireless device.

Below is a non-limiting example of how certain aspects of the proposed solutions could be implemented within the framework of a specific communication standard. In particular, the attached disclosures provide a non-limiting example of how the proposed solutions could be implemented within the framework of a 3 GPP TSG RAN standard. The changes described by the disclosures are merely intended to illustrate how certain aspects of the proposed solutions could be implemented in a particular standard. However, the proposed solutions could also be implemented in other suitable manners, both in the 3GPP Specification and in other specifications or standards. Introduction

One of the features of the new work item on enhancements of NB-loT is new UE power class, where the objective is

Specify the following features for enhancement of NB-IoT to achieve even lower device power consumption, while maintaining the coverage and capacity of the NB-loT network, and ultra-low UE cost

o Evaluate and, if appropriate, specify new UE power class(es) (e.g. 14dBm), and any necessary signaling support, to support lower maximum transmit power suitable for small form-factor batteries, with appropriate maximum coupling loss (MCL) relaxations compared to Rel-13.

In RAN4#80 a way forward was approved which states that

A reduction in maximum coupling loss shall be applied for UEs that adopt the lower transmit power class.

Companies are invited to evaluate the appropriate maximum output power for the new power class with MCL relaxation as compared to 164dB MCL.

For example: 164 - (23 - P) dB, whereas the reduction in MCL is (23-P), whereas P is the maximum transmission power of the new UE power class

The group will evaluate for example P = 14dBm as a starting point. Herein we discuss the new UE power class in the light of the previous agreements.

Discussion

In the following we look at different aspects of lower power UEs in NB-IoT

Required MCL

The work item description states that in the specifying the the new UE power class, appropriate MCL relaxation should be considered. The specified MCL for Rel-13 NB-IoT was around 164dB which is around 20 dB extension as compared to normal coverage in LTE. This coverage extension considers meters in deep basement. So depending on what kind of application is in mind, the MCL can be impacted. We consider two alternatives in MCL relaxation:

One alternative is the wearable applications with no coverage extension, i.e. MCL up to 144dB.

Another alternative is MCL relaxation that is proportional to the relaxation in UL output power. This means that the MCL is relaxed by

164-(23-P) dB,

where P is the maximum power of the new UE power class.

Proposal 1 : RAN4 should specify MCL= 164-(23-P) dB for the lower output power

UE

Capacity demand from a lower UE power class

In the following we present some system simulations for a system with path gain from GERAN Scenario 2, and traffic of 20 bytes downlink followed by 200 bytes response in uplink. In these simulation no connection setup, and random access was considered and only data was simulated. We consider in-band B-IoT carrier in LTE carrier 10 MHz with a total power of 40W without power boosting. Furthermore no PUSCH format 2, i.e. no ACK transmitted over PUSCH was considered, and we assumed ideal channel estimation. Receiver noise figures in downlink and uplink are 9dB and 5dB respectively.

In the following example we consider a coverage relaxation only corresponding to the

UE max power reduction as compared to 23dBm. This means that UEs that are above MCL=164-(23-P)dB are not allowed to access the system and not counted in the statistics. Figure 12 shows average UL resource utilization for different UE max output power values. As the figure shows by going down from 23dBm to 18dBm, the number of repetitions goes up by almost 30%, and if the UE maximum power is further lower at 14dBm the number of resources is increased by 50%. Also Figure 13 shows the packet delay for different UE power levels, and similarly by going to lower power of 18dBm and 14dBm the packet delay is increased by— 30% and— 40% roughly. If not relaxing the MCL it is clear that the increased resource usage is significant. Going from 23 to 14 dBm while maintaining the 164 dB MCL doubles the average number of repetitions and more than doubles the average transmission times.

However if the eNB knows the maximum power of the UE, by applying certain adjustment, the impact can be limited. Early indication of the UE power class removes unnecessarily many repetitions in the DL up until the eNB is informed that the target UE belongs to a different power class. Figure 12 shows UL resource utilization in terms of repetitions and Figure 13 shows Average total transmission length

Observation 1 : lowering maximum output power to 18dBm and 14dBm can result in an increase in resource usage by up to— 30% and— 40% respectively. However by early indication of the UE power class to the e B, the impact can be controlled.

Battery life

Another aspect that needs to be considered in the UE maximum output power is the form factor and lifetime of battery.

If the UE is in normal coverage mode, i.e. it does not run at its maximum output power, a lower output power means less power consumption. However for a UE in extended coverage mode, lower power results in longer transmission time, and therefore lower maximum power may result in higher power consumption. So depending on what coverage mode the UE is in, the battery life can be impacted positively or negatively.

Observation 2: Lowering maximum output power of the UE can impact the battery life positively or negatively. The impact needs to be evaluated.

Form factor

Lower UE output power and its implications on the size and cost of MTC devices was discussed in Rel-13 B-loT and Rel-13 eMTC. It was agreed that it is possible to integrate both baseband PAs with output power of up to 20dBm on the same chip as the rest of the baseband and analog part. Therefore from that point of view there seems to be no difference between different output power values of up to 20dBm.

Form factor of batteries also needs to be considered in this evaluation. Small size batteries such as coin cells can only deliver up to a certain drain current. Therefore depending on the type of application, the battery size and form need to be considered in the decision.

Indication of the new UE power class

As mentioned earlier if the eNB knows the maximum power of the UE, the impact can be limited by applying certain limitations. In order to efficiently use the UL and DL resources it is required that proper signaling is defined to inform the network about the maximum power of the UE. It is therefore proposed that a Liaison Statement (LS) should be sent to RAN1/RAN2 to consider indication of the UE power class to the eNB in order to handle UEs that belong to different power classes efficiently.

Proposal 2: It is proposed that an LS should be sent to RAN1/RAN2 to consider early indication of the UE power class to the eNB during the initial access procedure

Conclusions Herein we have studied the impacts of lower UE output power, and made the following observations and proposals:

Observation 1 : lowering maximum output power to 18dBm and 14dBm can result in an increase in resource usage by up to— 30% and— 40% respectively. However by early indication of the UE power class to the eNB, the impact can be controlled.

Observation 2: Lowering maximum output power of the UE can impact the battery life positively or negatively. The impact needs to be evaluated

Proposal 1 : RAN4 should specify MCL= 164-(23-P) dB for the lower output power

UE

Proposal 2: It is proposed that an LS should be sent to RAN1/RAN2 to consider early indication of the UE power class to the eNB

LS on new UE power class for Rel-14 NB-IoT

Overall Description:

RAN4 has studied the maximum power of the new UE power class and identified that in order to efficiently use the UL and DL resources, it is required that proper signaling is defined to inform the network about the maximum power of the UE.

Actions:

RAN4 respectfully request RANI and RAN2 to consider specifying signaling to indicate the UE power class to the eNB in order to handle UEs that belong to different power classes efficiently.

Although this disclosure has been described in terms of certain embodiments, alterations and permutations of the embodiments will be apparent to those skilled in the art. Although some embodiments have been described with reference to certain radio access technologies, any suitable radio access technology (RAT) or combination of radio access technologies may be used, such as long term evolution (LTE), LTE-Advanced, NR.,

UMTS, HSPA, GSM, cdma2000, WiMax, WiFi, etc. It will be appreciated that the foregoing description and the accompanying drawings represent non-limiting examples of the methods and apparatus taught herein. As such, the apparatus and techniques taught herein are not limited by the foregoing description and accompanying drawings. Instead, the embodiments herein are limited only by the following claims and their legal

equivalents.

Claims

1. A method performed by a network node serving a cell in a wireless network, the method comprising:

- sending (402) to a wireless device, an indication indicating whether partitioning of random access resources is used or not in the cell.

2. The method according to claim 1, further comprising

- partitioning (401) random access resources for the cell into one or more partitions, and sending (402) to the wireless device the indication comprises sending the indication indicating that partitioning of random access resources is used in the cell; and further comprising

- receiving (403) a random access message from the wireless device using a random access resource of the partitioned random access resources.

3. The method according to claim 2, wherein the indication indicating that partitioning of random access resources is used in the cell comprises information about one or more partitions of random access resources for the cell.

4. The method according to any of the claims 2-3, wherein the indication indicating that partitioning of random access resources is used in the cell comprises a range of preamble sequences for use by a particular power class of wireless devices.

5. The method according to any of the claims 2-4, wherein partitioning random access resources comprises partitioning the random access resources based on a frequency of access requests on certain partitions.

6. The method according to any of the claims 2-5, wherein partitioning random access resources comprises adapting a size of each partition of random access resources based on at least one of: prioritizing certain applications, improving cell throughput, and reducing access delay.

7. The method according to and of the claims 1-6, wherein sending the indication comprises sending the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

8. The method according to any of the claims 1-7, further comprising merging (404) the one or more partitions into a full set of random access resources; and sending to the wireless device, the indication indicating whether partitioning of random access resources is used or not in the cell comprises sending the indication indicating that partitioning is not used in the cell.

9. A method performed by a wireless device served in a cell of a network node in a wireless network, the method comprising:

obtaining (411) from the network node, an indication indicating whether partitioning of random access resources is used in the cell or not.

10. The method according to claim 9, wherein obtaining the indication comprises obtaining the indication indicating that partitioning of random access resources is used in the cell, and wherein the method further comprises:

transmitting (414) a random access message to the network node using a random access resource out of partitioned random access resources.

11. The method according to claim 10, wherein the indication indicating that partitioning of random access resources is used comprises information about one or more partitions of random access resources for the cell.

12. The method according to any of the claims 10-11, wherein the indication indicating that partitioning of random access resources is used comprises a range of preamble sequences for use by a particular power class of wireless devices.

13. The method according to any of the claims 10-12, further comprising

- selecting (412) one partition of partitioned random access resources based on an output power class of the wireless device; and

- selecting (413) the random access resource from the selected one partition.

14. The method according to claim 9, wherein the obtaining the indication indicating whether partitioning of random access resources is used in the cell or not comprises obtaining the indication that partitioning of random access resources is not used in the cell, and wherein the method further comprises: - selecting (415) a random access resource from a full set of random access resources; and transmitting (414) to the network node, a random access message to the network node using the selected random access resource out of the full set of random access resources.

15. The method according to any of the claims 9-14, wherein obtaining (411) the indication indicating whether partitioning of random access resources is used or not further comprises receiving the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

16. A network node configured to serve a cell in a wireless network, the network node being configured to:

send to a wireless device, an indication indicating whether partitioning of random access resources is used or not in the cell.

17. The network node according to claim 16, further being configured to

partition random access resources for the cell into one or more partitions, and configured to send the indication indicating that partitioning of random access resources is used in the cell; and further being configured to

receive a random access message from the wireless device (110) using a random access resource of the partitioned random access resources.

18. The network node according to claim 17, wherein the indication indicating that partitioning of random access resources is used in the cell comprises information about one or more partitions of random access resources for the cell.

19. The network node according to any of the claims 17-18, wherein the indication indicating that partitioning of random access resources is used in the cell comprises a range of preamble sequences for use by a particular power class of wireless devices.

20. The network node according to any of the claims 17-19, being configured to partition the random access resources based on a frequency of access requests on certain partitions.

21. The network node according to any of the claims 17-20, being configured to adapt a size of each partition of random access resources based on at least one of: prioritizing certain applications, improving cell throughput, and reducing access delay.

22. The network node according to and of the claims 16-21, being configured to send the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

23. The network node according to any of the claims 16-22, further being configured to merge the one or more partitions into a full set of random access resources; and then to send the indication indicating that partitioning is not used in the cell.

24. A wireless device (110) configured for a wireless network, which wireless network comprises a network node serving a cell in the wireless network, being configured to

obtain from the network node, an indication indicating whether partitioning of random access resources is used in the cell or not.

25. The wireless device (110) according to claim 24, being configured to obtain the indication indicating that partitioning of random access resources is used in the cell, and to

transmit a random access message to the network node using a random access resource out of partitioned random access resources.

26. The wireless device (110) according to claim 25, wherein the indication indicating that partitioning of random access resources is used comprises information about one or more partitions of random access resources for the cell.

27. The wireless device (110) according to any of the claims 25-26, wherein the indication indicating that partitioning of random access resources is used comprises a range of preamble sequences for use by a particular power class of wireless devices.

28. The wireless device (110) according to any of the claims 25-27, further being configured to

select one partition of partitioned random access resources based on an output power class of the wireless device; and to

select the random access resource from the selected one partition.

29. The wireless device (110) according to claim 24, being configured to obtain the indication that partitioning of random access resources is not used in the cell, and further configured to:

select a random access resource from a full set of random access resources; and to

transmit to the network node, a random access message to the network node using the selected random access resource out of the full set of random access resources.

30. The wireless device (110) according to any of the claims 24-29, being configured to receive the indication in at least one of: a master information block, MIB, a system information block, SIB, or a common control channel.

31. A computer program comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry out any of the methods according to any of the claims 1-15, as performed by the network node, or the wireless device.

32. A computer-readable storage medium, having stored thereon a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of the claims 1-15, as performed by the network node, or the wireless device.