WO2018073812A1 - Coverage extension frequency hopping scheme - Google Patents

Abstract

A method in a wireless communication network comprises determining a frequency hopping sequence for communication between a wireless device and a network node, the frequency hopping sequence being a function of a first hopping sequence and a second hopping sequence, wherein the first hopping sequence has a first frequency step size and a first sequence length, the second hopping sequence has a second frequency step size and a second sequence length, and the first frequency step size is greater than the second frequency step size, and communicating on frequencies selected according to the determined frequency hopping sequence.

Description

COVERAGE EXTENSION FREQUENCY HOPPING SCHEME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of US Provisional Patent Application No.

62/411,137 filed on October 21, 2016, the subject matter of which is hereby incorporated by reference.

TECHNICAL FIELD

[0002] The disclosed subject matter relates generally to telecommunications. Certain embodiments relate more particularly to concepts such as unlicensed spectrum, frequency hopping, LTE-Unlicensed (LTE-U), coverage extension, enhanced Machine Type

Communication (eMTC), frequency hopping, and Multefire.

BACKGROUND

[0003] The 3rd Generation Partnership Project (3 GPP) work on "Licensed-Assisted Access" (LAA) intends to allow Long Term Evolution (LTE) equipment to also operate in the unlicensed radio spectrum. Candidate bands for LTE operation in the unlicensed spectrum include 5 GHz, 3.5 GHz, among others. The unlicensed spectrum can be used as a complement to the licensed spectrum, but also allows completely standalone operation.

[0004] For the case of unlicensed spectrum used as a complement to the licensed spectrum, devices connect in the licensed spectrum (primary cell or PCell) and use carrier aggregation (CA) to benefit from additional transmission capacity in the unlicensed spectrum

(secondary cell or SCell). The CA framework allows a device to aggregate two or more carriers, with the condition that at least one carrier (or frequency channel) is in the licensed spectrum and at least one carrier is in the unlicensed spectrum. In the standalone (or completely unlicensed spectrum) mode of operation, one or more carriers are selected solely in the unlicensed spectrum.

[0005] Regulatory requirements, however, may not permit transmissions in the unlicensed spectrum without prior channel sensing, transmission power limitations or imposed maximum channel occupancy time. Since the unlicensed spectrum must be shared with other radios of similar or dissimilar wireless technologies, a so called listen-before-talk (LBT) method needs to be applied. LBT involves sensing the medium for a pre-defined minimum amount of time and backing off if the channel is busy. Due to the centralized coordination and dependency of terminal devices on the base-station (e.g., evolved NodeB (eNB)) for channel access in LTE operation and imposed LBT regulations, LTE uplink (UL) performance is especially hampered. UL transmission is becoming more important with user-centric applications and the need for pushing data to cloud.

[0006] Today, the unlicensed 5 GHz spectrum is mainly used by equipment implementing the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Wireless Local Area Network (WLAN) standard. This standard is known under its marketing brand "Wi-Fi" and allows completely standalone operation in the unlicensed spectrum. Unlike the case in LTE, Wi-Fi terminals can asynchronously access the medium and thus show better UL performance characteristics, especially in congested network conditions.

[0007] LTE uses OFDM in the downlink (DL) and Discrete Fourier Transform (DFT)- spread Orthogonal Frequency Division Multiplexing (OFDM) (also referred to as Single- Carrier Frequency Division Multiple Access (SC-FDMA)) in the UL.

[0008] FIG. 1 illustrates an example LTE DL physical resource. As shown in FIG. 1, the basic LTE DL physical resource can be seen as a time-frequency grid where each resource element corresponds to one OFDM subcarrier during one OFDM symbol interval. The UL subframe has the same subcarrier spacing as the DL and the same number of SC-FDMA symbols in the time domain as OFDM symbols in the DL.

[0009] FIG. 2 illustrates an example of the LTE time-domain structure. In the time domain, LTE DL transmissions are organized into radio frames of 10 ms. Each radio frame consists of ten equally-sized subframes of length Tsubframe = 1 ms, as shown in FIG. 2. Each subframe comprises two slots of duration 0.5 ms each, and the slot numbering within a frame ranges from 0 to 19. For normal cyclic prefix, one subframe consists of 14 OFDM symbols. The duration of each symbol is approximately 71.4 μβ.

[0010] Furthermore, the resource allocation in LTE is typically described in terms of resource blocks, where a resource block corresponds to one slot (0.5 ms) in the time domain and 12 contiguous subcarriers in the frequency domain. A pair of two adjacent resource blocks in the time direction (i.e., 1.0 ms) is known as a resource block pair. Resource blocks are numbered in the frequency domain, starting with 0 from one end of the system bandwidth.

[0011] DL transmissions are dynamically scheduled (i.e., in each subframe the base station transmits control information about which terminals data is transmitted to and upon which resource blocks the data is transmitted, in the current DL subframe). This control signaling is typically transmitted in the first 1, 2, 3 or 4 OFDM symbols in each subframe, and the number n = 1, 2, 3 or 4 is known as the Control Format Indicator (CFI). The DL subframe also contains common reference symbols, which are known to the receiver and used for coherent demodulation of, for example, the control information.

[0012] FIG. 3 illustrates an example DL subframe. More particularly, FIG. 3 illustrates a DL system with CFI = 3 OFDM symbols as control. The reference symbols shown in FIG. 3 are the cell-specific reference symbols (CRS) and are used to support multiple functions, including fine-time and frequency synchronization and channel estimation for certain transmission modes.

[0013] UL transmissions are dynamically scheduled (i.e., in each DL subframe the base station transmits control information about which terminals should transmit data to the eNB in subsequent subframes, and upon which resource blocks the data is transmitted). The UL resource grid is comprised of data and UL control information in the Physical Uplink Shared Channel (PUSCH), UL control information in the Physical Uplink Control Channel (PUCCH), and various reference signals such as demodulation reference signals (DMRS) and sounding reference signals (SRS). DMRS are used for coherent demodulation of PUSCH and PUCCH data, whereas SRS is not associated with any data or control information but is generally used to estimate the UL channel quality for purposes of frequency-selective scheduling.

[0014] FIG. 4 illustrates an example UL subframe. Note that UL DMRS and SRS are time- multiplexed into the UL subframe, and SRS are always transmitted in the last symbol of a normal UL subframe. The PUSCH DMRS is transmitted once every slot for subframes with normal cyclic prefix, and is located in the fourth and eleventh SC-FDMA symbols.

[0015] From LTE Release (Rel.) 11 onwards, DL or UL resource assignments can also be scheduled on the enhanced Physical Downlink Control Channel (EPDCCH). For Rel. 8 to Rel. 10, only the Physical Downlink Control Channel (PDCCH) is available. Resource grants are user equipment (UE) specific, and are indicated by scrambling the Downlink Control Information (DCI) Cyclic Redundancy Check (CRC) with the UE-specific Cell Radio Network Temporary Identifier (C-RNTI) identifier. A unique C-RNTI is assigned by a cell to every UE associated with it, and can take values in the range 0001-FFF3 in hexadecimal format. A UE uses the same C-RNTI on all serving cells.

[0016] The LTE Rel. 10 standard supports bandwidths larger than 20 MHz. One requirement on LTE Rel. 10 is to assure backward compatibility with LTE Rel. 8. This should also include spectrum compatibility. That would imply that an LTE Rel. 10 carrier, wider than 20 MHz, should appear as a number of LTE carriers to an LTE Rel. 8 terminal. Each such carrier can be referred to as a Component Carrier (CC). In particular for early LTE Rel. 10 deployments, it can be expected that there will be a smaller number of LTE Rel. 10-capable terminals compared to many LTE legacy terminals. Therefore, it is necessary to assure an efficient use of a wide carrier also for legacy terminals (i.e., that it is possible to implement carriers where legacy terminals can be scheduled in all parts of the wideband LTE Rel. 10 carrier). The straightforward way to obtain this would be by means of CA. CA implies that an LTE Rel. 10 terminal can receive multiple CCs, where the CCs have, or at least the possibility to have, the same structure as a Rel. 8 carrier.

[0017] FIG. 5 illustrates an example of carrier aggregation. A CA -capable UE is assigned a primary cell (PCell) which is always activated, and one or more secondary cells (SCells) which may be activated or deactivated dynamically.

[0018] The number of aggregated CCs as well as the bandwidth of the individual CC may be different for UL and DL. A symmetric configuration refers to the case where the number of CCs in DL and UL is the same, whereas an asymmetric configuration refers to the case where the number of CCs in DL and UL is different. Notably, the number of CCs configured in a cell may be different from the number of CCs seen by a terminal. A terminal may, for example, support more DL CCs than UL CCs, even though the cell is configured with the same number of UL and DL CCs.

[0019] In addition, a feature of CA is the ability to perform cross-carrier scheduling. This mechanism allows a (E)PDCCH on one CC to schedule data transmissions on another CC by means of a 3 -bit Carrier Indicator Field (CIF) inserted at the beginning of the

(E)PDCCH messages. For data transmissions on a given CC, a UE expects to receive scheduling messages on the (E)PDCCH on just one CC— either the same CC, or a different CC via cross-carrier scheduling. This mapping from (E)PDCCH to PDSCH is also configured semi-statically.

[0020] Internet-Of-Things (IoT) can be considered a fast evolving market within the telecommunications realm. Current 3GPP -based standards offer three different variants supporting IoT services: enhanced Machine-Type Communication (eMTC), Narrowband IoT (NB-IoT) and Extended Coverage Global Systems for Mobile Communications (EC-GSM). eMTC and NB-IoT have been designed using LTE as a baseline, with the main difference between the two being the minimum occupied bandwidth. eMTC and NB-IoT use 1.4 MHz and 180 kHz minimum bandwidth, respectively.

[0021] Both NB-IoT and eMTC have been designed with an operator deployment of macro cells in mind. Certain use cases where outdoor macro eNBs would communicate with IoT devices deep inside buildings are targeted, which require standardized coverage enhancement mechanisms.

[0022] 3GPP LTE Rel. 12 defined a UE power saving mode allowing long battery lifetime and a new UE category allowing reduced modem complexity. 3GPP Rel. 13 further introduced the eMTC feature, with a new UE category, Cat-M, that further reduces UE cost while supporting coverage enhancement. One element to enable cost reduction for Cat-M UE is to introduce a reduced UE bandwidth of 1.4 MHz in DL and UL within any system bandwidth (as described in 3GPP TR 36.888 vl2.0.0, "Study on provision of low-cost Machine-Type Communications (MTC) User Equipments (UEs) based on LTE (Rel. 12)" (hereinafter "TR 36.888")).

[0023] In LTE, the system bandwidth can be up to 20 MHz. This total bandwidth is divided into physical resource blocks (PRBs) of 180 kHz. Cat-M UEs with reduced UE bandwidth of 1.4 MHz only receive a part of the total system bandwidth at a time— a part corresponding to up to 6 PRBs. Herein, a group of 6 PRBs is referred to as a "PRB group."

[0024] In order to achieve the coverage targeted in LTE Rel. 13 for low -complexity UEs and other UEs operating delay tolerant MTC applications (as described in TR 36.888), time repetition techniques are used to allow energy accumulation of the received signals at the UE side. For physical data channels (e.g., PDSCH, PUSCH), subframe bundling (also known as transmission time interval (TTI) bundling) can be used. When subframe bundling is applied, each Hybrid Automatic Repeat Request (HARQ) (re transmission consists of a bundle of multiple subframes instead of just a single subframe. Repetition over multiple subframes are also applied to physical control channels.

[0025] Energy accumulation of the received signals involves several aspects. One of the main aspects involves accumulating energy for reference signals, for example by applying time-filters, in order to increase the quality of channel estimates used in the demodulation process. Another main aspect involves accumulation of demodulated soft-bits across repeated transmissions.

[0026] Unlicensed bands offer the possibility for deployment of radio networks by non- traditional operators that do not have access to licensed spectrum, such as building owners, industrial site and municipalities who want to offer a service within the operation they control. Recently, the LTE standard has been evolved to operate in unlicensed bands for the sake of providing mobile broadband using unlicensed spectrum. The 3GPP-based feature of LAA was introduced in Rel. 13, supporting CA between a primary carrier in licensed bands, and one or several secondary carriers in unlicensed bands. Further evolution of the LAA feature, which only supports DL traffic, was specified within the Rel. 14 feature of enhanced Licensed Assisted Access feLAA), which added the possibility to also schedule UL traffic on the secondary carriers. In parallel to the work within 3GPP Rel. 14, work within the MulteFire Alliance (MFA) aimed to standardize a system that would allow the use of standalone primary carriers within unlicensed spectrum. The resulting MulteFire 1.0 standard supports both UL and DL traffic.

[0027] Discussions regarding the potential to evolve existing unlicensed standards to also support IoT use-cases within unlicensed bands are currently ongoing, both within 3GPP as well as within MFA. Discussions within the MFA explicitly mention the opportunity for developing new standards that would have either of NB-IoT or eMTC as baseline. One issue to consider for such a design is regulatory requirements, which differ depending on frequency band and region.

[0028] One specific frequency band that may be eligible for IoT operation would be the band in the vicinity of 2.4 GHz. Requirements for the European region are specified within the European Telecommunications Standards Institute (ETSI) harmonized standard for equipment using wide band modulation, ETSI EN 300 328 V2.0.24, "Wideband

transmission systems; Data transmission equipment operating in the 2,4 GHz ISM band and using wide band modulation techniques; Harmonized Standard covering the essential requirements of E Directive 2014/53/EU" (hereinafter "ETSI EN 300 328"). Some requirements from ETSI EN 300 328 are discussed in the next section.

[0029] ETSI EN 300 328 provisions include several adaptivity requirements for different operation modes. From the top level, equipment can be classified either as frequency hopping or non-frequency hopping, as well as adaptive or non-adaptive. Adaptive equipment is mandated to sense whether the channel is occupied in order to better coexist with other users of the channel. The improved coexistence may come from, for example, LBT or detect and avoid (DAA) mechanisms. Non -frequency hopping equipment are subject to requirements on maximum power spectral density (PSD) of 10 dBm/MHz, which limits the maximum output power for systems using narrower bandwidths. Common for any of the adaptive schemes is the consequence that the receiving node will be unaware of the result of the sensing, and thus needs to detect whether signal is present or not. While such a signal detection most likely would be feasible for devices operating with moderate to high Signal to Interference plus Noise Ratios (SINR) levels, they may be infeasible for very low SINR levels.

[0030] For systems using repetition schemes to achieve coverage extension, the received SINR of each individual transmission is very low. Through accumulation of multiple transmissions, the effective SINR increases. However, in case the accumulation would include both signal as well as noise (as could be the case, for example, when the transmitter uses adaptive mechanisms), the repetition techniques may fail. One way of avoiding this would be to attempt detection of each individual repetition, although as already described this may not be feasible at the very low SINR levels targeted with these IoT standards. An IoT standard for 2.4 GHz in Europe may therefore be best devised by categorizing its devices as non-adaptive frequency hopping.

[0031] Requirements for non-adaptive frequency hopping include e.g. the following. First, a maximum on -time of 5 ms, which is required to be followed by a transmission gap. Second, a minimum duration of the transmission gap of 5 ms. Third, a maximum accumulated transmit time of 15 ms, which is the maximum total transmission time a node may be allowed to use before moving to the next frequency hop.

SUMMARY

[0032] In some embodiments of the disclosed subject matter, a method in a wireless communication network comprises determining a frequency hopping sequence for communication between a wireless device and a network node, the frequency hopping sequence being a function of a first hopping sequence and a second hopping sequence, wherein the first hopping sequence has a first frequency step size and a first sequence length, the second hopping sequence has a second frequency step size and a second sequence length, and the first frequency step size is greater than the second frequency step size, and communicating on frequencies selected according to the determined frequency hopping sequence. The method can be performed by e.g. the wireless device and/or the network node.

[0033] In certain related embodiments, the first frequency step size is greater than or equal to a frequency range covered by the second hopping sequence.

[0034] In certain related embodiments, the first frequency step size is less than a frequency range covered by the second hopping sequence.

[0035] In certain related embodiments, the hopping sequence is defined according to

nk,l ^{= m}k ^' $ + ^sk,l

[0036] where k represents a hop index of the first hopping sequence, / represents a hop index of the second hopping sequence, n_k ^l _l represents an z^'-th instance of a (k,l)-t frequency of the hopping sequence, m_k ^l represents an i-th instance of a k-th element of the first hopping sequence, S represents the first frequency step size, and s_{k l} represents an z^'-th instance of a (k,l)-t element of the second hopping sequence.

[0037] In certain related embodiments, the frequencies selected according to the determined frequency hopping sequence are disposed in unlicensed spectrum.

[0038] In certain related embodiments, the method further comprises, at the wireless device, performing channel estimation filtering across multiple frequency hops of the second hopping sequence. In some such embodiments, performing the channel estimation filtering comprises filtering channel estimates across a time duration that spans the multiple frequency hops of the second hopping sequence. In some such embodiments, the method further comprises, at the wireless device, determining a difference between a current and previous frequency of the wireless device, and in response to determining that the difference is larger than a first threshold, resetting at least one channel estimation filter. In some such embodiments, the method further comprises estimating a residual timing error.

[0039] In certain related embodiments, the method further comprises applying

compensation for residual timing errors.

[0040] In some embodiments of the disclosed subject matter, an apparatus for wireless communication comprises at least one processor, memory and transceiver collectively configured to perform a method such as that described above. The apparatus may be e.g. a wireless device or a network node.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings illustrate selected embodiments of the disclosed subject matter. In the drawings, like reference labels indicate like features.

[0042] FIG. 1 illustrates an example LTE DL physical resource.

[0043] FIG. 2 illustrates an example of the LTE time-domain structure.

[0044] FIG. 3 illustrates an example DL subframe [0045] FIG. 4 illustrates an example UL subframe.

[0046] FIG. 5 illustrates an example of carrier aggregation.

[0047] FIG. 6 illustrates an exemplary wireless communications network, in accordance with certain embodiments.

[0048] FIG. 7 illustrates an example of operating eMTC with UL and DL on the same channel, in accordance with certain embodiments.

[0049] FIG. 8 illustrates an example of operating eMTC with UL and DL on a pair of frequency channels, in accordance with certain embodiments.

[0050] FIG. 9 illustrates an example of transmission and frequency hopping sequence, in accordance with certain embodiments.

[0051] FIG. 10 illustrates a concept for design of frequency hopping sequences involving main and sub-hopping, in accordance with certain embodiments.

[0052] FIG. 11 illustrates an exemplary hopping sequence according to a hierarchical frequency hopping design, in accordance with certain embodiments.

[0053] FIG. 12 illustrates an example embodiment for the case of L = 7, in accordance with certain embodiments.

[0054] FIG. 13 illustrates an example embodiment for the case of L = 6, in accordance with certain embodiments.

[0055] FIG. 14 illustrates an example sub-hopping sequence with an arbitrary start frequency within the sequence of sub-hopping frequencies, in accordance with certain embodiments.

[0056] FIG. 15 is a flow chart illustrating a method in a wireless device, in accordance with certain embodiments.

[0057] FIG. 16 is a flow diagram of a method in a network node, in accordance with certain embodiments.

[0058] FIG. 17 is a flow diagram of a method in a network node, in accordance with certain embodiments.

[0059] FIG. 18 is a block schematic of an exemplary wireless device, in accordance with certain embodiments.

[0060] FIG. 19 is a block schematic of an exemplary network node, in accordance with certain embodiments.

[0061] FIG. 20 is a block schematic of an exemplary radio network controller or core network node, in accordance with certain embodiments. [0062] FIG. 21 is a block schematic of an exemplary wireless device, in accordance with certain embodiments.

[0063] FIG. 22 is a block schematic of an exemplary network node, in accordance with certain embodiments.

[0064] FIG. 23 is a flow diagram of a method in a wireless communication network, in accordance with certain embodiments.

DETAILED DESCRIPTION

[0065] The following description presents various embodiments of the disclosed subject matter. These embodiments are presented as teaching examples and are not to be construed as limiting the scope of the disclosed subject matter. For example, certain details of the described embodiments may be modified, omitted, or expanded upon without departing from the scope of the disclosed subject matter.

[0066] Certain embodiments are presented in recognition of shortcomings associated with conventional approaches, such as the following. The 3GPP Rel. 13 features of eMTC and NB-IoT facilitate coverage extension by repetition or bundling of transmitted control information or data transport blocks. On the receiver side, the signal is significantly affected by the high noise level associated with operation at high coupling loss. Channel estimates therefore need to be filtered across multiple sub-frames in order to facilitate demodulation.

[0067] Due to the requirements for operation of non-adaptive frequency hopping equipment in the 2.4 GHz band, channel estimate filtering may be limited because of the requirements on maximum accumulated transmit time, as the receiver may not be able to continue filtering past the point where the transmitter has performed a frequency hop.

[0068] Certain embodiments of the disclosed subject matter may address the above and other shortcomings. For instance, in some embodiments this is achieved by using a scheme for the definition of frequency hopping sequences that limits a maximum distance in frequency between subsequent frequency hops, thereby enabling receivers to attempt filtering of channel estimates across a time duration that spans more than one frequency hop. Such embodiments may assume that the underlying channel has a large enough coherence bandwidth such that the channel estimate on two adjacent frequencies is similar enough. The idea is thus two-fold: the first part pertains to the design of hopping sequences of the system, while the second part targets the UE behavior (i.e., methods to realize filtering of channel estimates across multiple frequency hops). The various embodiments described herein enable design of frequency hopping patterns that comply with spectrum regulations while simultaneously enabling UEs to improve their reception quality by employing filtering of estimates needed in the demodulation process across a time-period that spans multiple frequency hops.

[0069] According to one example embodiment, a method in a network node is disclosed. The network node determines a first hopping sequence where a difference in the corresponding frequency between two consecutive values is smaller than a first value. The network node determines a second hopping sequence. In certain embodiments, the difference in the corresponding frequency between two consecutive values for the second hopping sequence may be larger than the frequency range covered by the first hopping sequence. In certain embodiments, the difference in the corresponding frequency between two consecutive values for the second hopping sequence may be smaller than the frequency range covered by the first hopping sequence. The network node operates on a frequency corresponding to a function of the first and second hopping sequences. The above steps may advantageously aid channel estimation in a wireless device.

[0070] According to another example embodiment, a method in a wireless device for performing channel estimation in a frequency hopping scheme is disclosed. The wireless device determines a difference between a current frequency and a previous frequency the wireless device was operating on. The wireless device determines whether the difference between the current frequency and the previous frequency is larger than a first channel, and determines whether channel conditions require a reset. Upon determining either that the frequency difference is larger than the first threshold or that the channel conditions require a reset, the wireless device resets one or more channel estimation filters. In certain embodiments, the wireless device may apply a compensation for residual timing errors. The wireless device performs channel estimation filtering. In certain embodiments, the wireless device may estimate a residual timing error. The wireless device changes frequency according to a hopping pattern of the frequency hopping system.

[0071] Certain embodiments of the disclosed subject matter may provide one or more technical advantages. As one example, the combination of the various embodiments described herein and existing repetition techniques such as those introduced in, for example, the eMTC or NB-IoT standards, may advantageously enable a new IoT standard to operate at very low received SINR levels, even when frequency hopping is required. This in turn could increase coverage and allow for a lower density in the network deployment, ultimately reducing the deployment and operational cost. As another example, certain embodiments may advantageously aid channel estimation in a wireless device. Other advantages may be readily apparent to one having skill in the art. Certain

embodiments may have none, some, or all of the recited advantages.

[0072] FIG. 6 is a block diagram illustrating an embodiment of a network 100, in accordance with certain embodiments. Network 100 includes one or more UE(s) 110 (which may be interchangeably referred to as wireless devices 110) and one or more network node(s) 115 (which may be interchangeably referred to as eNBs 115). UEs 110 may communicate with network nodes 115 over a wireless interface. For example, a UE 110 may transmit wireless signals to one or more of network nodes 115, and/or receive wireless signals from one or more of network nodes 115. The wireless signals may contain voice traffic, data traffic, control signals, and/or any other suitable information. In some embodiments, an area of wireless signal coverage associated with a network node 115 may be referred to as a cell 125. In some embodiments, UEs 110 may have device-to-device (D2D) capability. Thus, UEs 110 may be able to receive signals from and/or transmit signals directly to another UE.

[0073] In certain embodiments, network nodes 115 may interface with a radio network controller. The radio network controller may control network nodes 115 and may provide certain radio resource management functions, mobility management functions, and/or other suitable functions. In certain embodiments, the functions of the radio network controller may be included in network node 115. The radio network controller may interface with a core network node. In certain embodiments, the radio network controller may interface with the core network node via an interconnecting network 120. Interconnecting network 120 may refer to any interconnecting system capable of transmitting audio, video, signals, data, messages, or any combination of the preceding. Interconnecting network 120 may include all or a portion of a public switched telephone network (PSTN), a public or private data network, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a local, regional, or global communication or computer network such as the Internet, a wireline or wireless network, an enterprise intranet, or any other suitable communication link, including combinations thereof.

[0074] In some embodiments, the core network node may manage the establishment of communication sessions and various other functionalities for UEs 110. UEs 110 may exchange certain signals with the core network node using the non-access stratum layer. In non-access stratum signaling, signals between UEs 110 and the core network node may be transparently passed through the radio access network. In certain embodiments, network nodes 115 may interface with one or more network nodes over an internode interface, such as, for example, an X2 interface.

[0075] As described above, example embodiments of network 100 may include one or more wireless devices 110, and one or more different types of network nodes capable of communicating (directly or indirectly) with wireless devices 110.

[0076] In some embodiments, the non-limiting term UE is used. UEs 110 described herein can be any type of wireless device capable of communicating with network nodes 115 or another UE over radio signals. UE 110 may also be a radio communication device, target device, D2D UE, machine-type-communication UE or UE capable of machine to machine communication (M2M), low-cost and/or low-complexity UE, a sensor equipped with UE, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), etc. UE 110 may operate under either normal coverage or enhanced coverage with respect to its serving cell. The enhanced coverage may be interchangeably referred to as extended coverage. UE 110 may also operate in a plurality of coverage levels (e.g., normal coverage, enhanced coverage level 1, enhanced coverage level 2, enhanced coverage level 3 and so on). In some cases, UE 110 may also operate in out-of-coverage scenarios.

[0077] Also, in some embodiments generic terminology, "radio network node" (or simply "network node") is used. It can be any kind of network node, which may comprise a base station (BS), radio base station, Node B, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, evolved Node B (eNB), network controller, radio network controller (RNC), base station controller (BSC), relay node, relay donor node controlling relay, base transceiver station (BTS), access point (AP), radio access point, transmission points, transmission nodes, Remote Radio Unit (RRU), Remote Radio Head (RRH), nodes in distributed antenna system (DAS), Multi-cell/multicast Coordination Entity (MCE), core network node (e.g., MSC, MME, etc.), O&M, OSS, SON, positioning node (e.g., E-SMLC), MDT, or any other suitable network node.

[0078] The terminology such as network node and UE should be considered non-limiting and does in particular not imply a certain hierarchical relation between the two; in general "eNodeB" could be considered as device 1 and "UE" device 2, and these two devices communicate with each other over some radio channel. [0079] Example embodiments of UE 110, network nodes 115, and other network nodes (such as radio network controller or core network node) are described in more detail below with respect to FIG. S 18-22.

[0080] Although FIG. 6 illustrates a particular arrangement of network 100, the various embodiments described herein may be applied to a variety of networks having any suitable configuration. For example, network 100 may include any suitable number of UEs 110 and network nodes 115, as well as any additional elements suitable to support communication between UEs or between a UE and another communication device (such as a landline telephone). Furthermore, although certain embodiments may be described as implemented in a Long Term Evolution (LTE) network, the embodiments may be implemented in any appropriate type of telecommunication system supporting any suitable communication standards (including 5G standards) and using any suitable components, and are applicable to any radio access technology (RAT) or multi-RAT systems in which a UE receives and/or transmits signals (e.g., data). For example, the various embodiments described herein may be applicable to LTE, LTE-Advanced, 5G, UMTS, HSPA, GSM, cdma2000, WCDMA, WiMax, UMB, WiFi, another suitable radio access technology, or any suitable combination of one or more radio access technologies. Although certain embodiments may be described in the context of wireless transmissions in the DL, the various embodiments are equally applicable in the UL.

[0081] As described above, the various embodiments described herein may advantageously enable the creation of frequency hopping patterns in a system operating in unlicensed bands. Certain embodiments may enable design of frequency hopping patterns that comply with spectrum regulations while simultaneously enabling UEs to improve their reception quality by employing filtering of estimates needed in the demodulation process across a time-period that spans multiple frequency hops.

[0082] In systems operating with frequency hopping, the transmitter and receiver hops synchronously according to a pre-determined pattern that has been made known to both transmitter and receiver. The actual sequence used could, for example, be signaled as part of the initial attachment sequence, or implicitly derived based on a function that depends on, for example, a transmitter ID, which in turn could be determined during an initial attachment procedure to the network or node. Different groups of devices may use different frequency hopping sequences, allowing re-use of the spectrum. [0083] There is 83.5 MHz available bandwidth in the 2.4 GHz unlicensed band. To operate LTE eMTC in this band, the available bandwidth is to be divided into a number of channels, each of the eMTC channel bandwidth of 1.4 MHz.

[0084] FIG. 7 illustrates an example of operating eMTC with UL and DL on the same channel, in accordance with certain embodiments. In a first mode of operating eMTC UL and DL on the same frequency channel, an exemplary design of the operating channels is illustrated in FIG. 7. There are 59 available channels for hopping. Each channel has a bandwidth of 1.4 MHz.

[0085] FIG. 8 illustrates an example of operating eMTC with UL and DL on a pair of frequency channels, in accordance with certain embodiments. In a second mode of operating eMTC UL and DL on a pair of frequency channels, an exemplary design of the operating channels is illustrated in FIG. 8. There are 29 available paired channels for hopping. Each channel has a bandwidth of 1.4 MHz.

[0086] FIG. 9 illustrates an example of transmission and frequency hopping sequence, in accordance with certain embodiments. Based on the requirements listed in Section 1.4 above (describing 2.4 GHz requirements for the European region and coverage extension), a pattern as shown in FIG. 9 could be devised that attempts to concentrate the DL signal as much as possible, while maximizing the time spent on each frequency hop, the dwell time. The example of FIG. 7 is a transmission and frequency hopping sequence that would be compliant with the non-adaptive frequency hopping option of ETSI EN 300 328.

[0087] A first example embodiment involves frequency hopping sequences based on a hierarchical design as shown in FIG. 10.

[0088] FIG. 10 illustrates a concept for design of frequency hopping sequences involving main and sub-hopping, in accordance with certain embodiments. In the example of FIG. 10, the frequency hopping sequence is further based on a main hopping sequence and a sub- hopping sequence. The main hopping sequence is designed to enable large frequency separation between hops. The main hopping sequence serves to randomize interference. The sub-hopping sequence is within each main hop. Within the sub-hopping sequence the frequency distance between two intermediate sub-hops is limited. The sub-hopping sequence serves the purpose of letting the UE filter channel estimates across multiple frequency hops, to enhance reception performance.

[0089] FIG. 11 illustrates an exemplary hopping sequence according to a hierarchical frequency hopping design, in accordance with certain embodiments. From the non-limiting exemplary embodiment illustrated in FIG. 11, it can be observed that the frequency separations between hops within a main hop duration are limited. This enables better channel estimation performance at the receiver. Between the main hops, large frequency separations are used to enable better interference randomization.

[0090] To support multiple operating eMTC-U networks, multiple such hierarchically designed frequency hopping sequences are designed. One such frequency hopping sequence is denoted as n_k ^l _l, where:

• i denotes a frequency sequence index. The total number of sequences is

denoted by / such that the range of ί is from 0 to /— 1.

• k denotes main hop index, ranging from 0 to T- 1. In the non-limiting example illustrated in FIG. U, K = 7.

• /denotes sub-hop index within each main hop ranging from 0 to L-\ . In the non-limiting example illustrated in FIG. 11, L = 8.

[0091] In some embodiments, the hopping sequence is calculated by the following equation (1):

where

• m_k ^l is an i-th main hopping sequence of length K,

• 5 is a frequency step size for the main hopping sequence,

• s_{k l} is a sub-hopping sequence of length L.

[0092] The sequence m_k' cm be defined as a pseudo-random sequence. In some embodiments, the sequence has the property that no value within the value range

[θ· · · (Κ - 1)] is occurring more than once. In some embodiments, cell ID and network ID are used to initialize a pseudo-random sequence generator.

[0093] In certain embodiments, the set of sequences m_k' are defined and standardized, and the selection of a specific sequence to use for transmission and reception is selected using a function that translates a physical cell ID (PCI) and a network ID to an index i within the set of sequences. The specific sequence to use m_k' is the direct result of a formula that takes physical cell ID (PCI) and a network ID as input and outputs a hopping sequence.

[0094] In certain embodiments, the frequency step size S for the main hopping sequence is set to be no less than the length of the sub-hopping sequence. That is, S≥ L. According to this setting, the frequency channel indices visited by a frequency hopping sequence n_k ^l _l are all distinct. One non -limiting embodiment is to set S = L.

[0095] In certain embodiments, the frequency step size for main hopping sequence S is set to a value smaller than the length of the sub-hopping sequence. That is, S < L. According to this setting, the frequency channel indices visited by a frequency hopping sequence n_k ^l _l may have repeated values. This design allows for longer main hopping sequences. That is, K can be larger. One non-limiting example embodiment is to set S = floor(JV /K), where N is the total number of available channels.

[0096] In certain embodiments, the sequence s_k ^l _l can be defined as a pseudo-random sequence. In one exemplary embodiment, the sequence has the property that no value within the value range is occurring more than once. In another exemplary embodiment, cell ID, network ID and the main hop index k are used to initialize a pseudo-random sequence generator.

[0097] In certain embodiments, the set of sequences s_{k l} are defined and standardized, and the selection of a specific sequence to use for transmission and reception is selected using a function that translates a physical cell ID (PCI), a network ID and the main hop index k to an index i within the set of sequences. The specific sequence to use s_k ^l _l is the direct result of a formula that takes physical cell ID (PCI), a network ID and the main hop index k as input and outputs a hopping sequence.

[0098] According to an example embodiment, the set of sequences s_{k l} are not dependent of the main hop index k. That is, for frequency hopping sequence n_k ^l the same s sequence is used across all main hops:

n_k ^l ,i = m_k ^l - S + s\

[0099] The s\ sequence can be determined based on physical cell ID (PCI), a network ID as described above.

[0100] According to another example embodiment, the set of sequences s_{k l} are dependent on only the main hop index k. That is, for different frequency hopping sequence n_k ^l the same s_{k x} sequence is used:

nk,l ^{= m}k ^' S + ^sk,l

[0101] The s_{k l} sequence can be determined based on the main hop index k as described above. [0102] According to still another example embodiment, the same s₍ sequence is used for all such hierarchically designed frequency hopping sequences:

n_k ^l ,i = m_k ^l - S + s_l

[0103] In one example embodiment, the sub-hopping sequence cycles through the indexes in increasing order. ¾ = / for I = 0,1,—, L— 1.

[0104] In another non-limiting exemplary embodiment, the sub-hopping sequence cycles through the index with an offset of 2 two indexes per hop. For example:

s, = 2l, for / < [ / 2]

s, = 2Z - 2/ - l, for l≥[L / 2 ]

[0105] FIG. 12 illustrates an example embodiment for the case of L = 7, in accordance with certain embodiments.

[0106] FIG. 13 illustrates an example embodiment for the case of L = 6, in accordance with certain embodiments.

[0107] FIG. 14 illustrates an example sub-hopping sequence with an arbitrary start frequency within the sequence of sub-hopping frequencies, in accordance with certain embodiments. According to the alternative non-limiting embodiment illustrated in FIG. 14, the sub- hopping sequence s₍ could be extended in a way that differs depending on the hopping sequence index and/or main hop index, k :

mod t

where o_k ^l is an offset that is determined by for frequency hopping sequence index ί and/or the main hop index k.

[0108] FIG. 15 is a flow chart illustrating a method in a wireless device, in accordance with certain embodiments. At initialization of the method at step 1502, the wireless device (for example, UE 1 10 described above in relation to FIG. 6) is operating on an arbitrary frequency within the frequency hopping cycle. The wireless device can thus determine whether or not the current operating frequency is associated with the first sub-hop within a main hop.

[0109] If at step 1502 the wireless device determines that the current operating frequency is the first sub-hop within a main hop, the method proceeds to step 1504, where the wireless device resets certain filters used in algorithms related to the demodulation process. A non- limiting example of such a filter would be the filtering of channel estimates. After resetting the filters at step 1504, the method proceeds to step 1510, described in more detail below.

[0110] If at step 1502 the wireless device determines that the current frequency is not associated with the first subhop of a main hop, the method proceeds to step 1506 where the wireless device makes an assessment of the channel conditions. The assessment of channel conditions may include, but is not limited to, one or more of Doppler estimation, RMS delay spread estimation and SINR estimation. In case channel conditions are such that it is beneficial to reset the filters, the method proceeds to step 1504, where the wireless device resets the filters. If at step 1506 the wireless device determines that channel conditions are such that the wireless device does not need to reset the filters, the wireless device avoids resetting the filters and the method proceeds to step 1508. In certain embodiments, at step 1508 the wireless device may apply a compensation related to a residual timing error. Regardless of whether the wireless device applies a compensation related to the residual timing error, the method proceeds to step 1510.

[0111] Regardless of whether or not the wireless device performed a reset of the filters, at step 1510 the wireless device performs filtering. In certain embodiments, the method proceeds to step 1512, where the wireless device may estimate a residual timing error. Regardless of whether the wireless device estimates residual timing error at step 1512, the method proceeds to step 1514, where the wireless device changes the frequency to the next frequency in the hopping sequence. The method then returns to step 1502, where the wireless device repeats the process described above.

[0112] Thus, the various embodiments described herein may advantageously enable the creation frequency hopping patterns in a system operating in unlicensed bands. The various embodiments described herein enable design of frequency hopping patterns that comply with spectrum regulations while simultaneously enabling wireless devices to improve their reception quality by employing filtering of estimates needed in the demodulation process across a time-period that spans multiple frequency hops.

[0113] FIG. 16 is a flow diagram of a method in a network node, in accordance with certain embodiments. The method begins at step 1604, where the network node determines a first hopping sequence where a difference in the corresponding frequency between two consecutive values is smaller than a first value.

[0114] At step 1608, the network node determines a second hopping sequence. In certain embodiments, a difference in the corresponding frequency between two consecutive values may be larger than a frequency range covered by the first hopping sequence. In certain embodiments, a difference in the corresponding frequency between two consecutive values may be smaller than a frequency range covered by the first hopping sequence.

[0115] At step 1612, the network node operates on a frequency corresponding to a function of the first and second hopping sequences.

[0116] FIG. 17 is a flow diagram of a method in a wireless device, in accordance with certain embodiments. The method begins at step 1704, where the wireless device determines a difference between a current frequency and a previous frequency the wireless device was operating on.

[0117] At step 1708, the wireless device determines whether the difference between the current frequency and the previous frequency is larger than a first threshold. At step 1712, the wireless device determines whether channel conditions require a reset.

[0118] At step 1716, upon determining either that the frequency difference is larger than the first threshold or that the channel conditions require a reset, the wireless device resets one or more channel estimation filters. In certain embodiments, the wireless device may apply a compensation for residual timing errors.

[0119] At step 1720, the wireless device performs channel estimation filtering. In certain embodiments, the wireless device may estimate a residual timing error.

[0120] At step 1724, the wireless device changes frequency according to a hopping pattern.

[0121] FIG. 18 is a block schematic of an exemplary wireless device, in accordance with certain embodiments. Wireless device 110 may refer to any type of wireless device communicating with a node and/or with another wireless device in a cellular or mobile communication system. Examples of wireless device 110 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-communication (MTC) device / machine-to-machine (M2M) device, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, a D2D capable device, or another device that can provide wireless communication. A wireless device 110 may also be referred to as UE, a station (STA), a device, or a terminal in some embodiments. Wireless device 110 includes transceiver 1810, processor 1820, and memory 1830. In some embodiments, transceiver 1810 facilitates transmitting wireless signals to and receiving wireless signals from network node 115 (e.g., via antenna 1840), processor 1820 executes instructions to provide some or all of the functionality described above as being provided by wireless device 110, and memory 1830 stores the instructions executed by processor 1820.

[0122] Processor 1820 may include any suitable combination of hardware and software implemented in one or more modules to execute instructions and manipulate data to perform some or all of the described functions of wireless device 110, such as the functions of wireless device 110 described above in relation to FIG.S 1-17. In some embodiments, processor 1820 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more applications, one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs) and/or other logic.

[0123] Memory 1830 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and/or other instructions capable of being executed by a processor. Examples of memory 1830 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, 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, data, and/or instructions that may be used by processor 1020.

[0124] Other embodiments of wireless device 110 may include additional components beyond those shown in FIG. 18 that may be 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). As just one example, wireless device 110 may include input devices and circuits, output devices, and one or more synchronization units or circuits, which may be part of the processor 1820. Input devices include mechanisms for entry of data into wireless device 110. For example, input devices may include input mechanisms, such as a microphone, input elements, a display, etc. Output devices may include mechanisms for outputting data in audio, video and/or hard copy format. For example, output devices may include a speaker, a display, etc.

[0125] FIG. 19 is a block schematic of an exemplary network node, in accordance with certain embodiments. Network node 115 may be any type of radio network node or any network node that communicates with a UE and/or with another network node. Examples of network node 115 include an eNodeB, a node B, a base station, a wireless access point (e.g., a Wi-Fi access point), a low power node, a base transceiver station (BTS), relay, donor node controlling relay, transmission points, transmission nodes, remote RF unit (RRU), remote radio head (RRH), multi-standard radio (MSR) radio node such as MSR BS, nodes in distributed antenna system (DAS), O&M, OSS, SON, positioning node (e.g., E-SMLC), MDT, or any other suitable network node. Network nodes 115 may be deployed throughout network 100 as a homogenous deployment, heterogeneous deployment, or mixed

deployment. A homogeneous deployment may generally describe a deployment made up of the same (or similar) type of network nodes 115 and/or similar coverage and cell sizes and inter-site distances. A heterogeneous deployment may generally describe deployments using a variety of types of network nodes 115 having different cell sizes, transmit powers, capacities, and inter-site distances. For example, a heterogeneous deployment may include a plurality of low-power nodes placed throughout a macro-cell layout. Mixed deployments may include a mix of homogenous portions and heterogeneous portions.

[0126] Network node 115 may include one or more of transceiver 1910, processor 1920, memory 1930, and network interface 1940. In some embodiments, transceiver 1910 facilitates transmitting wireless signals to and receiving wireless signals from wireless device 110 (e.g., via antenna 1950), processor 1920 executes instructions to provide some or all of the functionality described above as being provided by a network node 115, memory 1930 stores the instructions executed by processor 1920, and network interface 1940 communicates signals to backend network components, such as a gateway, switch, router, Internet, Public Switched Telephone Network (PSTN), core network nodes or radio network controllers 130, etc.

[0127] Processor 1920 may include any suitable combination of hardware and software implemented in one or more modules to execute instructions and manipulate data to perform some or all of the described functions of network node 115, such as those described above in relation to FIG.S 1-17 above. In some embodiments, processor 1920 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more applications, and/or other logic.

[0128] Memory 1930 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and/or other instructions capable of being executed by a processor. Examples of memory 1930 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, 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.

[0129] In some embodiments, network interface 1940 is communicatively coupled to processor 1920 and may refer to any suitable device operable to receive input for network node 115, send output from network node 115, perform suitable processing of the input or output or both, communicate to other devices, or any combination of the preceding. Network interface 1940 may include appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network.

[0130] Other embodiments of network node 115 may include additional components beyond those shown in FIG. 19 that may be responsible for providing certain aspects of the radio network node's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solutions 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.

[0131] FIG. 20 is a block schematic of an exemplary radio network controller or core network node 130, in accordance with certain embodiments. Examples of network nodes can include a mobile switching center (MSC), a serving GPRS support node (SGSN), a mobility management entity (MME), a radio network controller (RNC), a base station controller (BSC), and so on. The radio network controller or core network node 130 includes processor 2020, memory 2030, and network interface 2040. In some embodiments, processor 2020 executes instructions to provide some or all of the functionality described above as being provided by the network node, memory 2030 stores the instructions executed by processor 2020, and network interface 2040 communicates signals to any suitable node, such as a gateway, switch, router, Internet, Public Switched Telephone Network (PSTN), network nodes 115, radio network controllers or core network nodes 130, etc.

[0132] Processor 2020 may include any suitable combination of hardware and software implemented in one or more modules to execute instructions and manipulate data to perform some or all of the described functions of the radio network controller or core network node 130. In some embodiments, processor 2020 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more applications, and/or other logic.

[0133] Memory 2030 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and/or other instructions capable of being executed by a processor. Examples of memory 2030 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, 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.

[0134] In some embodiments, network interface 2040 is communicatively coupled to processor 2020 and may refer to any suitable device operable to receive input for the network node, send output from the network node, perform suitable processing of the input or output or both, communicate to other devices, or any combination of the preceding. Network interface 2040 may include appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network.

[0135] Other embodiments of the network node may include additional components beyond those shown in FIG. 20 that may be 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).

[0136] FIG. 21 is a block schematic of an exemplary wireless device, in accordance with certain embodiments. Wireless device 110 may include one or more modules. For example, wireless device 110 may include a determining module 2110, a communication module 2120, a receiving module 2130, an input module 2140, a display module 2150, and any other suitable modules. In some embodiments, one or more of determining module 2110, communication module 2120, receiving module 2130, input module 2140, display module 2150, or any other suitable module may be implemented using one or more processors, such as processor 1820 described above in relation to FIG. 18. Wireless device 110 may perform the methods related to coverage extension frequency hopping schemes described above with respect to FIG. S 1-17. [0137] Determining module 2110 may perform the processing functions of wireless device 110. For example, determining module 2110 may determine a difference between a current frequency and a previous frequency the wireless device was operating on. As another example, determining module 2110 may determine whether the difference between the current frequency and the previous frequency is larger than a first threshold. As still another example, determining module 2110 may determine whether channel conditions require a reset. As yet another example, determining module 2110 may, upon determining either that the frequency difference is larger than the first threshold or that the channel conditions require a reset, reset one or more channel estimation filters. As another example, determining module 2110 may perform channel estimation filtering using the reset one or more channel estimation filters. As another example, determining module 2110 may change frequency according to a hopping pattern of the frequency hopping system. As still another example, determining module 2110 may apply a compensation for residual timing errors. As yet another example, determining module 2110 may estimate a residual timing error.

[0138] Determining module 2110 may include or be included in one or more processors, such as processor 1820 described above in relation to FIG. 18. Determining module 2110 may include analog and/or digital circuitry configured to perform any of the functions of determining module 2110 and/or processor 2120 described above. The functions of determining module 2110 described above may, in certain embodiments, be performed in one or more distinct modules.

[0139] Communication module 2120 may perform the transmission functions of wireless device 110. Communication module 2120 may transmit messages to one or more of network nodes 115 of network 100. Communication module 2120 may include a transmitter and/or a transceiver, such as transceiver 1810 described above in relation to FIG. 18. Communication module 2120 may include circuitry configured to wirelessly transmit messages and/or signals. In particular embodiments, communication module 2120 may receive messages and/or signals for transmission from determining module 2110. In certain embodiments, the functions of communication module 2120 described above may be performed in one or more distinct modules.

[0140] Receiving module 2130 may perform the receiving functions of wireless device 110. Receiving module 2130 may include a receiver and/or a transceiver, such as transceiver 1810 described above in relation to FIG. 18. Receiving module 2130 may include circuitry configured to wirelessly receive messages and/or signals. In particular embodiments, receiving module 2130 may communicate received messages and/or signals to determining module 2110. In certain embodiments, the functions of receiving module 2130 described above may be performed in one or more distinct modules.

[0141] Input module 2140 may receive user input intended for wireless device 110. For example, the input module may receive key presses, button presses, touches, swipes, audio signals, video signals, and/or any other appropriate signals. The input module may include one or more keys, buttons, levers, switches, touchscreens, microphones, and/or cameras. The input module may communicate received signals to determining module 2110.

[0142] Display module 2150 may present signals on a display of wireless device 110.

Display module 2150 may include the display and/or any appropriate circuitry and hardware configured to present signals on the display. Display module 2150 may receive signals to present on the display from determining module 2110.

[0143] Determining module 2110, communication module 2120, receiving module 2130, input module 2140, and display module 2150 may include any suitable configuration of hardware and/or software. Wireless device 110 may include additional modules beyond those shown in FIG. 21 that may be responsible for providing any suitable functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the various solutions described herein).

[0144] FIG. 22 is a block schematic of an exemplary network node 115, in accordance with certain embodiments. Network node 115 may include one or more modules. For example, network node 115 may include determining module 2210, communication module 2220, receiving module 2230, and any other suitable modules. In some embodiments, one or more of determining module 2210, communication module 2220, receiving module 2230, or any other suitable module may be implemented using one or more processors, such as processor 1920 described above in relation to FIG. 19. In certain embodiments, the functions of two or more of the various modules may be combined into a single module. Network node 115 may perform the methods related to coverage extension frequency hopping schemes described above with respect to FIGS. 1-17.

[0145] Determining module 2210 may perform the processing functions of network node 115. For example, determining module 2210 may determine a first hopping sequence where a difference in the corresponding frequency between two consecutive values is smaller than a first value. As another example, determining module 2210 may determine a second hopping sequence. As still another example, determining module 2210 may operate on a frequency corresponding to a function of the first and second hopping sequences.

[0146] Determining module 2210 may include or be included in one or more processors, such as processor 1920 described above in relation to FIG. 19. Determining module 2210 may include analog and/or digital circuitry configured to perform any of the functions of determining module 2210 and/or processor 1920 described above. The functions of determining module 2210 may, in certain embodiments, be performed in one or more distinct modules.

[0147] Communication module 2220 may perform the transmission functions of network node 115. As one example, communication module 2220 may operate on a frequency corresponding to a function of the first and second hopping sequences. Communication module 2220 may transmit messages to one or more of wireless devices 110.

Communication module 2220 may include a transmitter and/or a transceiver, such as transceiver 1910 described above in relation to FIG. 19. Communication module 2220 may include circuitry configured to wirelessly transmit messages and/or signals. In particular embodiments, communication module 2220 may receive messages and/or signals for transmission from determining module 2210 or any other module. The functions of communication module 2220 may, in certain embodiments, be performed in one or more distinct modules.

[0148] Receiving module 2230 may perform the receiving functions of network node 115. For example, receiving module 2230 may operate on a frequency corresponding to a function of the first and second hopping sequences. Receiving module 2230 may receive any suitable information from a wireless device. Receiving module 2230 may include a receiver and/or a transceiver, such as transceiver 1910 described above in relation to FIG. 19. Receiving module 2230 may include circuitry configured to wirelessly receive messages and/or signals. In particular embodiments, receiving module 2230 may communicate received messages and/or signals to determining module 2210 or any other suitable module. The functions of receiving module 2230 may, in certain embodiments, be performed in one or more distinct modules.

[0149] Determining module 2210, communication module 2220, and receiving module 2230 may include any suitable configuration of hardware and/or software. Network node 115 may include additional modules beyond those shown in FIG. 22 that may be responsible for providing any suitable functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the various solutions described herein).

[0150] FIG. 23 is a flow diagram of a method 2300 in a wireless communication network, in accordance with certain embodiments. This method could be performed, for instance, by a wireless device and/or network node as described above. The method involves

communication, according to a determined frequency hopping sequence, which could be accomplished, e.g., by transmitting and/or receiving according to the sequence.

[0151] Referring to FIG. 23, the method comprises determining a frequency hopping sequence for communication between a wireless device and a network node, the frequency hopping sequence being a function of a first hopping sequence and a second hopping sequence, wherein the first hopping sequence has a first frequency step size and a first sequence length, the second hopping sequence has a second frequency step size and a second sequence length, and the first frequency step size is greater than the second frequency step size (S2305), and communicating on frequencies selected according to the determined frequency hopping sequence (S2310). An example of the first hopping sequence is the main hopping sequence described above, which has a relatively large frequency step size such as that between consecutive clusters of dots illustrated FIG. 11, and an example of the second hopping sequence is the sub-hopping sequence described above, which has a relatively small frequency step size such as that between consecutive dots illustrated in FIG. 11. The function of the first hopping sequence and the second hopping sequence may be, for instance, a scaled combination of the first and second hopping sequences that repeats over time, as illustrated by equation (1).

[0152] In some embodiments, the first frequency step size is greater than or equal to a frequency range covered by the second hopping sequence. For instance, in the example of FIG. 1 1, the label "R" indicates an example of the frequency range covered by the second hopping sequence, and the label "S" indicates an example of the first frequency step size that is equal to "R". Alternatively, the first frequency step size may be less than the frequency range covered by the second hopping sequence. For instance, in the example of FIG. U S could alternatively be less than R.

[0153] In some embodiments, the hopping sequence is defined according to equation (1) as follows:

nk,l ^{= m}k ^' $ + ^sk,l [0154] where k represents a hop index of the first hopping sequence, / represents a hop index of the second hopping sequence, n_k ^l _l represents an z^'-th instance of a (k,l)-t frequency of the hopping sequence, m_k ^l represents an i-th instance of a k-th element of the first hopping sequence, S represents the first frequency step size, and s_{k l} represents an z^'-th instance of a (k,l)-t element of the second hopping sequence.

[0155] In some embodiments, the frequencies selected according to the determined frequency hopping sequence are disposed in unlicensed spectrum. Such frequencies could also be used in other contexts, such as eMTC or eMTC-U systems, Multefire systems, IoT systems, etc.

[0156] In some embodiments, the method further comprises the wireless device performing channel estimation filtering across multiple frequency hops of the second hopping sequence. In general, the purpose of channel estimation filtering is to decrease the effects of noise and interference on channel estimates. The receiver filters (in time and/or frequency) raw channel estimates based on known reference symbols. The filtering is typically done over units in time where the channel can be assumed to be fairly constant, which is assumed to be the case within the second hopping sequence.

[0157] In some embodiments, performing the channel estimation filtering comprises filtering channel estimates across a time duration that spans the multiple frequency hops of the second hopping sequence.

[0158] In some embodiments, the method further comprises the wireless device determining a difference between a current and previous frequency of the wireless device, and in response to determining that the difference is larger than a first threshold, resetting at least one channel estimation filter. In this context, resetting a channel estimation filter generally entails discarding any states representing previous channel estimates and preparing the filter to process new raw channel estimates.

[0159] In some embodiments, the method further comprises estimating a residual timing error and/or applying compensation for residual timing errors. In this context, estimating a residual timing error can be done e.g. by estimating the max or center of gravity of the power delay profile of the channel and the compensation for residual timing errors can be done by applying a phase ramp in frequency corresponding to the estimated residual timing error to the raw channel estimates prior to filtering. [0160] Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the disclosure. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components.

Additionally, operations of the systems and apparatuses may be performed using any suitable logic comprising software, hardware, and/or other logic. As used in this document, "each" refers to each member of a set or each member of a subset of a set.

[0161] Modifications, additions, or omissions may be made to the methods described herein without departing from the scope of the disclosure. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.

[0162] Abbreviations used in this description may include the following.

3 GPP 3rd Generation Partnership Project

AP Access Point

BS Base Station

BSC Base Station Controller

BSR Buffer Status Request

BTS Base Transceiver Station

CA Carrier Aggregation

CC Component Carrier

CCA Clear Channel Assessment

CDM Code Division Multiplexing

CFI Control Format Indicator

CPE Customer Premises Equipment

CQI Channel Quality Information

CRC Cyclic Redundancy Check

C-RNTI Cell Radio Network Temporary Identifier

CRS Cell- Specific Reference Signal

D2D Device-to-device

DAA Detect and Avoid

DAS Distributed Antenna System

DCI Downlink Control Information

DFT Discrete Fourier Transform

DL Downlink DMRS Demodulation Reference Signal

DMTC DRS Measurement Timing Configuration

DRS Discovery Reference Signal

eLAA enhanced Licensed-Assisted Access

eMTC Enhanced Machine-Type Communication eNB evolved Node B, base station

EPDCCH Enhanced Physical Downlink Control Channel

ETSI European Telecommunications Standards Institute

FDD Frequency Division Duplex

HARQ Hybrid Automatic Repeat Request

IEEE Institute of Electrical and Electronics Engineers

IoT Internet-of-Things

LAA Licensed-Assisted Access

LAN Local Area Network

LBT Listen Before Talk

LEE Laptop Embedded Equipment

LME Laptop Mounted Equipment

LTE Long Term Evolution

LTE-U LTE in Unlicensed Spectrum

M2M Machine-to-Machine

MAN Metropolitan Area Network

MCE Multi -cell/multicast Coordination Entity

MCS Modulation level and coding scheme

MFA MulteFire Alliance

MIMO Multiple Input Multiple Output

MSR Multi-standard Radio

NAS Non-Access Stratum

NB Narrowband

NB-IoT Narrowband Internet-of-Things

OFDM Orthogonal Frequency Division Multiplexing

PCell Primary Cell

PDCCH Physical Downlink Control Channel

PDSCH Physical Downlink Shared Channel PMI Precoding Matrix Indicator

PRB Physical Resource Block

PSD Power Spectral Density

PSTN Public Switched Telephone Network

PUSCH Physical Uplink Shared Channel

PUCCH Physical Uplink Control Channel

RAT Radio Access Technology

RB Resource Block

RNC Radio Network Controller

RNTI Radio Network Temporary Identifier

RRC Radio Resource Control

RRH Remote Radio Head

RRU Remote Radio Unit

SCell Secondary Cell

SC-FDMA Single-Carrier Frequency Division Multiple Access

SINR Signal to Interference plus Noise Ratio

SRS Sounding Reference Signal

STA Station

TDD Time Division Duplex

TFRE Time Frequency Resource Element

TTI Transmission Time Interval

TXOP Transmission Opportunity

UCI Uplink Control Information

UE User Equipment

UL Uplink

WAN Wide Area Network

WLAN Wireless Local Area Network

[0163] Although the disclosed subject matter has been presented in terms of certain embodiments, alterations and permutations of the embodiments will be apparent to tliose skilled in the art. Accordingly, the above description of the embodiments does not constrain this disclosure. Other changes, substitutions, and alterations are possible without departing from the scope of this disclosure, as defined by the following claims.

Claims

CLAIMS:

1. A method in a wireless communication network (100), comprising:

determining a frequency hopping sequence for communication between a wireless device and a network node, the frequency hopping sequence being a function of a first hopping sequence and a second hopping sequence, wherein the first hopping sequence has a first frequency step size and a first sequence length, the second hopping sequence has a second frequency step size and a second sequence length, and the first frequency step size is greater than the second frequency step size (S2305); and

communicating on frequencies selected according to the determined frequency hopping sequence (S2310).

2. The method of claim 1, wherein the first frequency step size is greater than or equal to a frequency range covered by the second hopping sequence.

3. The method of claim 1, wherein the first frequency step size is less than a frequency range covered by the second hopping sequence.

4. The method of any of claims 1-3, wherein the hopping sequence is defined according to

nk,l ^{= m}k ^' $ + ^sk,l

where k represents a hop index of the first hopping sequence, / represents a hop index of the second hopping sequence, n_k ^l _l represents an z^'-th instance of a (/ J)-th frequency of the hopping sequence, m_k ^l represents an i-th instance of a k-th element of the first hopping sequence, S represents the first frequency step size, and s_{k l} represents an z^'-th instance of a (k,l)-t element of the second hopping sequence.

5. The method of any of claims 1-4, wherein the frequencies selected according to the determined frequency hopping sequence are disposed in unlicensed spectrum.

6. The method of any of claims 1-5, wherein the method is performed at the wireless device.

7. The method of any of claims 1-5, wherein the method is performed at the network node.

8. The method of any of claims 1-7, further comprising, at the wireless device, performing channel estimation filtering across multiple frequency hops of the second hopping sequence.

9. The method of claim 8, wherein performing the channel estimation filtering comprises filtering channel estimates across a time duration that spans the multiple frequency hops of the second hopping sequence.

10. The method of claim 8, further comprising, at the wireless device, determining a difference between a current and previous frequency of the wireless device, and in response to determining that the difference is larger than a first threshold, resetting at least one channel estimation filter.

11. The method of claim 8, further comprising estimating a residual timing error.

12. The method of claim 8, further comprising applying compensation for residual timing errors.

13. An apparatus for wireless communication, comprising:

at least one processor (1820, 1920), memory (1830, 1930) and transceiver (1810, 1910) collectively configured to:

determine a frequency hopping sequence for communication between a wireless device and a network node, the frequency hopping sequence being a function of a first hopping sequence and a second hopping sequence, wherein the first hopping sequence has a first frequency step size and a first sequence length, the second hopping sequence has a second frequency step size and a second sequence length, and the first frequency step size is greater than the second frequency step size (S2305); and

communicate on frequencies selected according to the determined frequency hopping sequence (S2310).

14. The apparatus of claim 13, wherein the first frequency step size is greater than or equal to a frequency range covered by the second hopping sequence.

15. The method of claim 13, wherein the first frequency step size is less than a frequency range covered by the second hopping sequence.

16. The apparatus of any of claims 13-15, wherein the hopping sequence is defined according to

nk,l ^{= m}k ^' $ + ^sk,l

where k represents a hop index of the first hopping sequence, / represents a hop index of the second hopping sequence, n_k ^l _l represents an z^'-th instance of a (/ J)-th frequency of the hopping sequence, m_k ^l represents an i-th instance of a k-th element of the first hopping sequence, S represents the first frequency step size, and s_{k l} represents an z^'-th instance of a (k,l)-t element of the second hopping sequence.

17. The apparatus of any of claims 13-16, wherein the frequencies selected according to the determined frequency hopping sequence are disposed in unlicensed spectrum.

18. The apparatus of any of claims 13-17, wherein the apparatus is the wireless device.

19. The apparatus of any of claims 13-18, wherein the apparatus is the network node.

20. The apparatus of any of claims 13-18, wherein the at least one processor, memory and transceiver are further collectively configured to, at the wireless device, perform channel estimation filtering across multiple frequency hops of the second hopping sequence.

21. The apparatus of claim 20, wherein performing the channel estimation filtering comprises filtering channel estimates across a time duration that spans the multiple frequency hops of the second hopping sequence.

22. The apparatus of claim 20, wherein the at least one processor, memory and transceiver are further collectively configured to, at the wireless device, determine a difference between a current and previous frequency of the wireless device, and in response to determining that the difference is larger than a first threshold, reset at least one channel estimation filter.

23. The apparatus of claim 20, wherein the at least one processor, memory and transceiver are further collectively configured to estimate a residual timing error.

24. The apparatus of claim 20, wherein the at least one processor, memory and transceiver are further collectively configured to apply compensation for residual timing errors.