WO2019032087A1

WO2019032087A1 - Multi-mode retransmission scheme for wireless networks

Info

Publication number: WO2019032087A1
Application number: PCT/US2017/045760
Authority: WO
Inventors: Stephan Saur; Silvio MANDELLI; Thorsten Wild
Original assignee: Nokia Solutions And Networks Oy; Nokia Usa Inc.
Priority date: 2017-08-07
Filing date: 2017-08-07
Publication date: 2019-02-14

Abstract

A technique includes transmitting data from a first network node to a second network node within a wireless network; retransmitting, one or more times during a first phase, the data from the first network node to the second network node using a first retransmission mode; detecting a condition; switching, by the first network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; and retransmitting, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode.

Description

Multi-Mode Retransmission Scheme For Wireless Networks

TECHNICAL FIELD

[0001 ] This description relates to communications.

BACKGROUND

[0002] A communication system may be a facility that enables

communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is an architecture that is being standardized by the 3^rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node AP (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments.

[0004] A global bandwidth shortage facing wireless carriers has motivated the consideration of the underutilized millimeter wave (mmWave) frequency spectrum for future broadband cellular communication networks, for example. mmWave (or extremely high frequency) may, for example, include the frequency range between, e.g., 30 and 300 gigahertz (GHz). Radio waves in this band may, for example, have wavelengths from ten to one millimeters, giving it the name millimeter band or millimeter wave. The amount of wireless data will likely significantly increase in the coming years. Various techniques have been used in attempt to address this challenge including obtaining more spectrum, having smaller cell sizes, and using improved technologies enabling more bits/s/Hz. One element that may be used to obtain more spectrum is to move to higher frequencies, e.g., above 6 GHz. For fifth generation wireless systems (5G), an access architecture for deployment of cellular radio equipment employing mmWave radio spectrum has been proposed. Other example spectrums may also be used, such as, e.g., cmWave radio spectrum (2-30 GHz).

[0005] In many cases, wireless communication systems may suffer from one or more impairments that may limit the signal-to-interference plus noise ratio (SINR). Some example impairments may include channel fading, path loss, interference from other users, and receiver noise. Consequently, data packets sent from one network node (e.g., user device/UE) to another network node may not be reliably received at another point or network node (e.g., an access point or a base station). In some cases, each data packet may be decoded only with a certain probability depending on the instantaneous SINR and the utilized link parameters (e.g., transmit power, coding rate, ... ).

SUMMARY

[0006] According to an example implementation, a method comprising:

transmitting data from a first network node to a second network node within a wireless network; retransmitting, one or more times during a first phase, the data from the first network node to the second network node using a first retransmission mode; detecting a condition; switching, by the first network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; and retransmitting, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode.

[0007] According to an example implementation, an apparatus includes at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to: transmit data from a first network node to a second network node within a wireless network;

retransmit, one or more times during a first phase, the data from the first network node to the second network node using a first retransmission mode; detect a condition; switch, by the first network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; and retransmit, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode. [0008] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: transmitting data from a first network node to a second network node within a wireless network;

retransmitting, one or more times during a first phase, the data from the first network node to the second network node using a first retransmission mode; detecting a condition; switching, by the first network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; and retransmitting, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode.

[0009] According to an example implementation, a method comprising:

attempting to receive, by a second network node within a wireless network during a first phase, data that was retransmitted from a first network node based on a first retransmission mode; detecting a condition; switching, by the second network node in response to the detected condition, a retransmission mode from the first

retransmission mode to a second retransmission mode that is different from the first retransmission mode; And, attempting to receive, by the second network node during a second phase, data that was retransmitted from the first network node based on the second retransmission mode.

[0010] According to an example implementation, an apparatus includes at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to: attempt to receive, by a second network node within a wireless network during a first phase, data that was retransmitted from a first network node based on a first retransmission mode; detect a condition; switch, by the second network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; And, attempt to receive, by the second network node during a second phase, data that was retransmitted from the first network node based on the second retransmission mode.

[0011 ] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: attempting to receive, by a second network node within a wireless network during a first phase, data that was retransmitted from a first network node based on a first retransmission mode; detecting a condition; switching, by the second network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; And, attempting to receive, by the second network node during a second phase, data that was retransmitted from the first network node based on the second retransmission mode.

[0012] The details of one or more examples of implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a block diagram of a wireless network according to an example implementation.

[0014] FIG. 2 is a diagram illustrating operation of a system according to an example implementation.

[0015] FIG. 3 is a diagram illustrating an example of a hybrid retransmission scheme with reactive switching according to an example implementation.

[0016] FIG. 4 is a diagram illustrating an example of a hybrid retransmission scheme with proactive switching according to an example implementation.

[0017] FIG. 5 is a diagram illustrating a hybrid retransmission scheme with a reactive switching according to another example implementation.

[0018] FIG. 6 is a diagram illustrating a probability mass function (PMF) of a successful transmission latency with different retransmission modes/schemes according to an example implementation.

[0019] FIG. 7 is a diagram illustrating a Cumulative Density Function (CDF) of the sum of the occupied bandwidth in all transmissions for a single packet according to an example implementation.

[0020] FIG. 8A is a flow chart illustrating operation of a network node according to an example implementation.

[0021 ] FIG. 8B is a flow chart illustrating operation of a network node according to another example implementation. [0022] FIG. 9 is a block diagram of a node or wireless station (e.g., base station/access point or mobile station/user device) according to an example

implementation.

DETAILED DESCRIPTION

[0023] FIG. 1 is a block diagram of a wireless network 130 according to an example implementation. In the wireless network 130 of FIG. 1, user devices 131, 132, 133 and 135, which may also be referred to as mobile stations (MSs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB), a gNB (which may be a 5G base station) or a network node. At least part of the functionalities of an access point (AP), base station (BS) or (e)Node B (eNB) may be also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices 131, 132, 133 and 135. Although only four user devices are shown as being connected or attached to BS 134, any number of user devices may be provided. BS 134 is also connected to a core network 150 via a SI interface 151. This is merely one simple example of a wireless network, and others may be used.

[0024] A user device (user terminal, user equipment (UE)) may refer to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and/or touch screen computer, a tablet, a phablet, a game console, a notebook, and a multimedia device, as examples. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. Also, UEs may also be provided within a number of different technologies or applications, such as sensors, actuators, machines, vehicles, etc.

[0025] In addition, the phrase network node may be used herein to describe any network node within a wireless network, such as either a user device or UE, or a base station (BS) or access point (AP). As used in various examples described herein, a transmitting network node may be a network node that is transmitting data, while a receiving network node is a network node that is receiving the data, in that particular example. Although both transmitting and receiving network nodes may typically transmit and receive information (e.g., data, control signals).

[0026] In LTE (as an example), core network 150 may be referred to as Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility /handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks.

[0027] The various example implementations may be applied to a wide variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G (New Radio, or NR), ultra-reliability low latency communications (URLLC), Internet of Things (IoT), cmWave, and/or mmWave band networks, or any other wireless network. LTE, 5G, cmWave and mmWave band networks are provided only as illustrative examples, and the various example implementations may be applied to any wireless technology/wireless network.

[0028] In many cases, wireless communication systems may suffer from one or more impairments that may limit the signal-to-noise-plus-interference ratio (SINR). Some example impairments may include channel fading, path loss, interference from other users, and receiver noise. Consequently, data packets sent from one network node (e.g., user device/UE) to another network node may not be reliably received at another point or network node (e.g., an access point or a base station). In some cases, each data packet may be decoded only with a certain probability depending on the instantaneous SINR and the utilized link parameters (e.g., transmit power, coding rate, ... ). Hence, many services may demand re-transmissions of corrupted packets to increase reliability at the price of the increased latency introduced by the retransmission scheme. Depending on the radio technology, certain procedures are available for that purpose, e.g. Hybrid Automatic Repeat Request (HARQ) with Chase Combining or Incremental Redundancy may be used to retransmit data packets.

[0029] In an example implementation, 5G (New Radio) may address or at least consider three example use case families, and one of these use cases is Ultra- Reliable Low-Latency Communications (URLLC). An example requirement for this type of service is to deliver a packet successfully with a very high probability (e.g., 99.9999999%) within a stringent delay threshold (e.g., 1 ms). According to an example implementation, a technique that may be used to achieve these goals for URLLC may include the exploitation of diversity, which may include, for example, sending multiple copies of the same information using different radio resources (time, frequency, code domain), using different propagation channels (space domain, multi- link) or even different technologies (multi RAT). A drawback of using such diversity techniques to improve reliability and delay may be a relatively low or poor efficiency with respect to spectrum and energy. In most cases, multiple copies of the same information are not needed at all, and the spent resources are wasted. Thus, many cellular standards are based on efficient and fast re-transmission of corrupted packets only when this is actually needed. For example, if the transmitting device receives a negative acknowledgement (NACK) or no feedback at all after a certain time has passed from the transmission attempt, it may initiate a retransmission.

[0030] However, in many cases, the overall number of possible retransmissions may be limited due to a particular latency threshold or latency budget for a service (e.g., for URLLC or other use case or service), and the round-trip time required to receive feedback from the receiving network node and then retransmit the data. This in turn affects the achievable level of reliability. The more transmission attempts that are possible, then the higher is the probability of a successful reception of the data, but typically at a significantly higher delay or latency.

[0031 ] According to an example implementation, one or more retransmission modes may be used to retransmit data, including at least the following for example.

[0032] 1) NACK-based retransmission mode: A Hybrid Automatic Repeat Request (HARQ) scheme may be used to trigger a fast retransmission on the lower layers of the protocol stack. The basic idea is that the receiver feeds back an indication of successful (ACK) or unsuccessful (NACK) decoding of the data packet in a well-defined point in time. In case of a NACK, the transmitting network node transmits a second representation of the failed data packet. This can be a repetition of the packet in order to allow soft combining of both attempts at the receiver, or, more advanced, additional redundancy (or redundancy version) that lowers the code rate, and consequently improves the probability for successful decoding of the extended packet (first transmission plus additional redundancy of the second transmission). The main advantage of the NACK-based retransmission mode is that re-transmissions occur only if necessary (e.g., only in response to a NACK, or other explicit request for retransmission, for example). The main disadvantage is the delay due to the

ACK/NACK feedback, caused by the HARQ Round Trip Time (RTT) after the transmission. For URLLC, there may be fewer opportunities to retransmit data. So in some cases, a NACK-based retransmission mode may create too much latency for multiple retransmissions for URLLC or other high reliability services. Thus, for services or use cases with a very low latency budget, it may not be possible to use (or limited retransmission times for) NACK-based retransmission mode to retransmit data, e.g., where some of the retransmissions may extend beyond the latency budget. Thus, while NACK-based retransmission mode may provide efficient spectral efficiency (e.g., retransmit only when needed), this retransmission mode may not provide very high reliability due to relatively long RTT.

[0033] 2) Blind retransmission mode: this retransmission mode may include retransmission of the data packet without an explicit request in a predefined time- frequency pattern. Typically, either the same data packet is just repeated one or more times and combined at the receiver to maximize the SINR, or the transmitted packets are the ones that would be transmitted with a HARQ scheme. For example, in some example blind retransmission modes, either the number of repetitions

(retransmissions) is predefined or the data retransmissions may continue until an ACK is received. The main advantage of the blind retransmission mode is the low or minimal delay in transmitting multiple copies of the data. The transmitter doesn't wait for the feedback (e.g., NACK) until it retransmits the data packet - so the HARQ RTT delay is avoided or circumvented. The main drawback is the relatively poor spectral efficiency. If system operates at a target packet error rate of 10%, the majority of the retransmissions are actually not needed, leading to poor resource efficiency. Thus, for example, in a blind retransmission mode, without waiting for any reply (or NACK) from receiver, the transmitter would retransmit the data one or more times. In many cases, blind retransmission may be unnecessary, but the transmitter does not know in advance which packets will need to be retransmitted, so blind retransmission mode may include retransmitting every data packet multiple (or one or more) times, e.g., every TTI for one or more TTIs. According to an example implementation, the number of retransmissions for a blind retransmission mode may be known in advance by both transmitting network node (transmitter) and receiving network node

(receiver), may be indicated by control signaling (from one of the network nodes to one or more other network nodes) to indicate or agree on number of retransmissions, or the transmitter may retransmit data as many times as necessary until transmitter receives an ACK from receiver indicating that receiver received the data packet. A drawback of the blind retransmission mode is a very inefficient use of radio resources, but this mode can provide very high reliability.

[0034] Therefore, example implementations are described to provide a flexible scheme with the purpose of improving or optimizing the trade-off between an efficient usage of resources on the one hand, and the possibility to schedule enough re-transmissions (to improve reliability) if this is needed on the other hand.

[0035] Example implementations are described that may combine usage of multiple retransmission modes, e.g., based on different conditions or events that may be detected at either a transmitting network node (UE or BS) or a receiving network node (BS or UE). Different retransmission modes may use different techniques for retransmitting data (e.g., different triggers or mechanisms to cause a retransmission of data), and may have different advantages and disadvantages (e.g., different delays or latencies, and/or may be associated with different spectral efficiency). According to illustrative example implementations, a multi-phase retransmission scheme may be provided that uses multiple retransmission modes, wherein the multiple

retransmission modes may include, for example: 1) a negative acknowledgement (NACK)-based retransmission mode in which a first network node (e.g., a transmitting network node) retransmits the data (e.g., which may be the same data or a different redundancy version of the data) to a second network node (e.g., a receiving network node) in response to receiving a NACK from the second network node; and, 2) a blind retransmission mode in which the first network node retransmits (e.g., one or more times, depending on the configuration) the data (e.g., which may be the same data or a different redundancy version of the data) to the second network node without receiving (or without waiting to receive) an explicit retransmission request. For example, the blind retransmission mode may include the first network node retransmitting data, even though the first network node has not received (and without waiting to receive) feedback (e.g., the first network node has not received a NACK) for the data from the second network node, and/or without waiting for an expiration of a transmission timer at the first network node (e.g., where ordinarily an expiration of such transmission timer associated with a data without receiving an

ACK/acknowledgement or NACK may cause the first network node to retransmit the data). Thus, for example, the blind retransmission mode may involve the first network node retransmitting the data before any ACK/NACK feedback has been received from the second network node with respect to such data. [0036] Thus, according to an example implementation, an example technique may include transmitting data from a first network node to a second network node within a wireless network; retransmitting, one or more times during a first phase, the data from the first network node to the second network node using a first

retransmission mode; detecting a condition; switching, by the first network node in response to the detected condition, a retransmission mode from the first

retransmission mode to a second retransmission mode that is different from the first retransmission mode; and retransmitting, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode.

[0037] Thus, by way of illustrative example, the first network node may use a NACK-based retransmission mode initially to perform one or more retransmissions of the data. Thus, in this manner, the first network node may perform a number of ACK/NACK transmissions (e.g., including transmissions and retransmissions in the NACK-based retransmission mode). Then, when a condition is detected, the first network node may switch retransmission modes to the blind retransmission mode and then retransmit, one or more times, the data using the blind retransmission mode. Alternatively, a network node may begin with a blind retransmission mode, and then may switch to the NACK-based retransmission mode.

[0038] A NACK-based retransmission mode, or a blind retransmission mode may correspond to a slot, a subframe (both in 3GPP LTE or NR terminology), a so- called mini-slot (in 3GPP NR terminology) or a transmission time interval (TTI).

[0039] As noted, the first network node may switch transmission modes for the data from a first retransmission mode to a second retransmission mode in response to a detected condition. There are a number of different conditions (or triggers or events) that may cause the first network node to switch retransmission modes. For example, the first (e.g., transmitting) network node may switch retransmission modes based on one or more of the following, by way of some illustrative examples:

[0040] 1) Based on a latency budget for the data (e.g., based on a maximum latency for the service, e.g., for URLLC). The first network node may determine a latency budget for data depending on the QoS flag associated to the specific transmission (e.g., 1 ms for a specific URLLC type). Thus, for example, when an amount of time has elapsed (e.g., since some reference point, such as the initial data transmission) that is a threshold percentage (e.g., 60%) of the latency budget for the data, this may cause the first network node to switch modes, e.g., from the NACK- based retransmission mode to the blind retransmission mode. Thus, if a latency budget for data is 5 ms, the first network node may, if an ACK has not been received yet, begin using the blind retransmission mode after 3 ms (60% of 5 ms) have elapsed, or when only 2 ms of the latency budget remains, so as to apply more resources to ensure the successful transmission of the data. Note that the switching may depend also on the absolute amount the time missing before the latency budget, rather than the threshold percentage mentioned above. For instance, the switching can be set to happen always 1 round trip time before the latency budget, e.g. -0.572 ms in case of 0.143 ms TTI when the round trip time consists of 4 TTIs.

[0041 ] 2) Based on a number of ACK/NACK retransmissions performed by the first network node. Thus, for example, after an initial data transmission and two ACK/NACK retransmissions (e.g., a retransmission in response to a received NACK for the data or a failure to receive an ACK/NACK), the first network node may then switch to a blind retransmission mode for any further (one or more) retransmissions of the data, e.g., until either expiration of the latency budget for the data or until an ACK is received for the data from the second network node.

[0042] 3) The first network node may receive a mode switch signal from the second network node that instructs the first network node to switch retransmission modes from the first retransmission mode to the second retransmission mode. Thus, for example, the first network node may switch retransmission modes from a first retransmission mode to a second retransmission mode in response to a received mode switch signal from the second network node. The mode switch signal may, for example, indicate the retransmission mode to use or switch to.

[0043] Thus, for example, a flexible hybrid retransmission scheme is provided that may include at least two phases, each phase represented by its own retransmission mode. For example, in a first phase, a NACK-based retransmission mode may be applied, e.g., where the receiver (receiving network node) explicitly asks for a retransmission (by sending a NACK). In a second phase, when approaching the latency threshold of the service (e.g., URLLC service or other service), a blind retransmission mode is applied. In this manner, a hybrid retransmission scheme may be used, which may provide advantages of both retransmission modes. For example, initially, a spectral efficient retransmission mode (e.g., NACK-based retransmission mode) may be used to retransmit data only when requested, in order to conserve resources. However, if the first retransmission mode is unsuccessful in transmitting the data to the receiving network node, and as the latency budget is approached, it may now be more important to (in those cases where a data transmission has not yet succeeded) allocate more resources in order to ensure a higher probability that a successful transmission of the data is accomplished, even at the expense of requiring greater network resources. Thus, in such a situation where data has not yet been received and decoded at the receiver via a first phase (e.g., using NACK-based retransmission mode), the transmitting network node and receiving network node may then switch to a second retransmission mode (e.g., a blind retransmission mode). In at least some (or many) cases of course, the data may be successfully transmitted via the first phase and the first retransmission mode (e.g., using the NACK-based

retransmission mode during a first phase), thus avoiding use of the second

retransmission mode (e.g., a blind retransmission mode) during the second phase (where the second retransmission mode may be less efficient, but may also provide a higher reliability, than the first retransmission mode). Thus, in this manner, according to an example implementation, a hybrid retransmission scheme may initially allow a first retransmission mode to be used for retransmission of data during a first phase. And, for example, only in the case where the use of that first retransmission mode during a first phase is unsuccessful in transmitting the data, then the transmitter and receiver may switch to a second retransmission mode, e.g., to use a different retransmission technique(s) and/or to provide an improved probability and improved reliability for data transmission.

[0044] In a first illustrative example, because the transmitter is not near or within a threshold time of the end of the latency budget, the transmitter and receiver may begin with a NACK-based retransmission mode to transmit and then retransmit the data to the receiver. At some point (e.g., when 70% of the latency budget has been used, or when some number of transmissions and retransmissions have occurred without successful delivery of the data), the transmitter and receiver may switch to the blind retransmission mode. According to the blind retransmission mode,

retransmissions may be performed one or many times, e.g., every TTI, until a predetermined number of retransmissions has been reached or until an ACK has been received that acknowledges receipt of the data. [0045] In a second illustrative example, a UE may initially be located in a basement or other location with weak or challenging signal conditions. Based on these network conditions (e.g., received signal strength, or signal quality from a BS), and based on a relatively high QoS required for this service, the transmitter/UE may select a blind transmission scheme to begin with, and may signal or request this retransmission mode to the BS (or the BS may select this retransmission mode for the UE to use, and signal the UE). The UE, using the blind retransmission scheme may transmit the data multiple times to the BS, but does not receive an ACK. At some point, the signal conditions for the UE dramatically improve based on movement of the UE to a better location. Based on these improved signal conditions between the UE and the BS, the UE switches (or is instructed to switch by the BS) to a NACK- based retransmission mode, and the data is then transmitted by the UE, and awaits a NACK, before retransmitting the data. The UE may continue retransmitting the data in response to each received NACK, e.g., until a threshold number of retransmissions has been reached or an expiration of the latency budget for the service. These are merely some illustrative example, and other examples may be used.

[0046] FIG. 2 is a diagram illustrating operation of a system according to an example implementation. As shown in FIG. 2, a transmitting network node 220 may transmit data to a receiving network node 210. Initially, nodes 220 and 210 are operating in a NACK-based retransmission mode. A data packet is first transmitted at 232 from node 220 to node 210, but is not decoded by node 210 (the X indicates a failed data transmission). At 234, node 210 sends a NACK, since the expected data packet is not received and decoded by node 210. Upon receipt of NACK 234, the node 220 retransmits the data at 236, in accordance with the NACK-based retransmission mode., but this retransmitted data at 236 is also not received (as indicated by the X). At 238, node 220 switches to a blind retransmission mode in which the data will be retransmitted, e.g., every TTI. As shown in FIG. 2, according to this illustrative example of a blind retransmission mode, the node 220 retransmits the data 7 times (e.g., a retransmission every TTI), beginning with the retransmission at 238. The retransmission 240 is received and decoded by the node 210, and the node 210 sends an ACK at 242. Upon receipt of the ACK at 242, the transmitting network node 220 ceases or discontinues the blind retransmission of the data. In an example implementation, node 238 may switch to a blind retransmission mode immediately after receiving NACK 234. [0047] According to an example implementation(s), switching between multiple retransmission modes may be performed. There may be different conditions or triggers that may cause a node to switch or change retransmission modes. Some illustrative examples A) - D) are briefly described below.

[0048] A) Reactive switching: In an example implementation, a node may react to a specific event by switching retransmission modes. For example, a transmitter communicates in a new dedicated field in a scheduling request (or exploiting a dedicated QoS information) a latency budget. Then, the scheduler (provided at the BS/receiver) is able to communicate to the transmitter if the transmitter should switch from the NACK-based retransmission mode to the blind retransmission mode. For example, a mode switch signal may be provided or carried in a new field in the NACK message. In a first example case, for UL data transmission (data from UE to BS), the UE transmits data, and the BS can convey both a NACK and a mode switch signal together to UE, e.g., send a NACK message with a control field requesting the transmitter/UE to switch modes to the blind retransmission mode (e.g., in this example, the BS may keep track of latency budget for data and determines when to switch retransmission modes, e.g., the scheduler in BS may manage this process); In a second example case, for DL data transmission (data from BS to UE), the UE sends a NACK, and the BS decides to switch retransmission mode to blind retransmission mode for downlink data transmission, and then BS sends control information (e.g., a new message or control information in DCI, maybe provide the mode switch signal with scheduling resource allocation (for DL transmission) to UE indicating a switch to the blind mode (provided by BS to UE within the DCI), e.g., where DCI from BS could include both a mode switch signal and DL resource allocation for DL transmission). See FIG. 3 for an example of reactive switching.

[0049] B) Proactive switching: (see FIG. 4 for an example of proactive switching). Proactive switching may involve switching retransmission modes after a predetermined number of transmissions or retransmissions or after a predetermined period of data or a predetermined portion of latency budget has been used. For example, the transmitter, based on QoS, may decide based in time or based on a predetermined number of transmissions, when the transmitter will switch modes, e.g., prior to the first transmission in contrast to the reactive scheme. The transmitter may communicate in a new dedicated field e.g., in the scheduling request, or in a DL (downlink) resource allocation, (or in other message) the number of transmissions N it will perform in the NACK-based retransmission modes before switching to the blind retransmission mode. Then, the transmitter (and receiver) autonomously switches to the blind retransmission mode after the indicated number (N) of transmissions or retransmissions, for example. Thus, in this illustrative example, the transmitter may transmit to the receiver an indicated number of transmissions (N) to be used for a first retransmission mode, and then both transmitter and receiver will switch for any subsequent retransmissions. The transmitter may, for example, indicate a number of retransmissions or a certain point in time where transmitter will switch to second retransmission mode, or it may be known in advance by both transmitter and receiver that N retransmission attempts will be performed before switching retransmission modes. The Proactive scheme may include a case where the transmitted information may communicate the total time during which the first retransmission mode/scheme must be used (e.g. 1 ms for the NACK-based retransmissions) before switching to the second retransmission mode/scheme (e.g. blind retransmission mode).

[0050] C) A Dynamic decision of the UE according to QoS parameters or battery constraints. In this example, a battery status (or change in batter status) of the transmitter may cause a change in retransmission modes. For example, if battery level of a transmitting network node drops below a threshold, then the transmitting network node may signal the receiving network node a change from blind

retransmission mode to a NACK-based retransmission mode, e.g., in order to save power/battery resources at the transmitter. If battery is plugged in, and battery status improves, then subsequent data transmissions may be transmitted via the blind retransmission mode again, e.g., if QoS conditions at transmitting network node or receiving network node require more frequent retransmissions for successful data delivery.

[0051 ] D) Configuration-based switching: This may be an example of proactive switching. In configuration-based switching, the BS may communicate general HARQ configuration (e.g., maximum retransmission number, number of parallel HARQ processes, amount of bandwidth) to the UE, e.g., using a RRC message such as RRC ReconfigurationMessage indicating the number of regular NACK-based transmissions/retransmissions and the number of final blind

retransmissions. HARQ configuration could also indicate number of

transmissions/retransmissions with first mode, and then switch to second mode. [0052] In general, control signalling may be used to communicate a mode switch signal from a first network node to a second network node. The mode switch signal may be communicated, e.g., via existing control signals, RRC signalling, HARQ configuration; via resource allocation/scheduling information, piggy backed on a NACK, or via other signalling or messages.

[0053] According to an example implementation, example inventive hybrid schemes may achieve a high reliability (e.g., matching the QoS requirements as in the blind retransmission mode), while providing a much more efficient use of resources (e.g., such efficiency may be only slightly worse than NACK-based retransmission). Moreover, this illustrative scheme is flexible and may be tuned to properly target the requirements in term of latency/reliability properties or requirements of each different QoS flow or a particular latency budget.

[0054] FIG. 3 is a diagram illustrating an example of a hybrid retransmission scheme with reactive switching according to an example implementation. As shown in FIG. 3, a transmitter 310 (e.g., a UE) may transmit data to a receiver 320 (e.g., a BS, with a scheduler). Two phases are shown, including a first phase 330 in which a NACK-based retransmission mode is used, and a second phase 340 in which a blind retransmission mode is used. At 352, transmitter 310 transmits a scheduling request along with a QoS flag, e.g., where the QoS flag may indicate a QoS (and/or a latency budget) of the data or service for this data flow. This QoS flag may inform the receiver 320 of the required QoS for the service flow and/or the latency budget for the service flow. For example, the required/requested QoS for this service flow may be used by the scheduler of the BS/receiver 320 to determine when to switch

retransmission modes from the NACK-based retransmission mode to the blind retransmission mode. The Scheduler of the BS/receiver 320 may monitor the quality of service that is provided to the transmitter, e.g., to determine whether the requested/required QoS is being provided, and if not, then this may cause the receiver 320 to send a message to transmitter to change retransmission modes. At 354, receiver 320 sends a resource grant to transmitter 310, and at 356 the transmitter 310 transmits a first data transmission (1^st Tx) via such resource, but this data at 356 is not decoded by the receiver 320 (as indicated by the dashed line). At 358, receiver 320 sends a NACK, which causes a second transmission (2^nd Tx) to be transmitted, which is not received and decoded at receiver 320. At this point, the scheduler/receiver 320 makes a decision to switch retransmission modes, e.g., in order to provide the required or requested QoS. Thus, at 360, the receiver 320 sends a NACK (with respect to 2^nd Tx data) and a switch flag that is a mode switch signal to request the transmitter to switch retransmission modes. Transmitter 310 receives the NACK and switch flag, and switches to a blind retransmission mode, causing the transmitter 310 to transmit the data at every opportunity, e.g., at every TTI, (without receiving any further NACKS/feedback) multiple data transmissions, including 3^rd Tx, 4^th Tx, 5^th Tx, ...

[0055] FIG. 4 is a diagram illustrating an example of a hybrid retransmission scheme with proactive switching according to an example implementation. In this illustrative example shown in FIG. 4, a transmitter 310 may be transmitting data to a receiver 320. The retransmission of data may include a first phase 430 in which a NACK-based retransmission mode is used to improve spectral efficiency, and a second phase 440 in which a blind retransmission mode is used to match service requirements for the service flow. At 410, transmitter 310 transmit a scheduling request, which includes a value N=2 that indicates a number of transmissions and retransmissions in the NACK-based retransmission mode, before there will be a switch to the blind retransmission mode. At 412, the receiver/BS provides a grant to allocate or provide uplink resources. The transmitter 310 then transmits data (1^st Tx), but this is not received or decoded by the receiver 320. At 414, a NACK is sent by receiver 320. Likewise, a NACK-based retransmission (2^nd Tx) of the data (in response to NACK 414) is also not received by receiver, causing receiver 320 to send another NACK 416. Because the value N=2 of NACK-based

transmissions/retransmissions has been performed, the transmitter 310 and receiver 320 (e.g., based on scheduling request at 410 which provided the value N=2) know that transmitter 310 will now change to the blind retransmission mode, e.g., for 3^rd Tx, 4^th Tx, 5^th Tx, ...

[0056] FIG. 5 is a diagram illustrating a hybrid retransmission with a reactive switching according to another example implementation. A Mobile Station (MS, or UE, the Transmitter) sends a data packet in uplink to a Base Station (BS - the

Receiver). In this example, the transmitter has requested a service with the stringent requirements to deliver the data packet successfully within 20 ms. A TTI may be of length of 1ms, for example. The initial re-transmission scheme is the NACK-based, i.e., the BS indicates a failed decoding attempt with a NACK at a specified point in time, e.g. 4 TTIs after the uplink transmission. In this example, at least three transmission attempts are necessary because the first two transmission attempts in TTIs 0 and 8 are responded with NACKs in TTIs 4 and 12, respectively. In a conventional HARQ scheme, a single third packet would be sent solely in TTI 16. In case of unsuccessful reception, the service will fail because the 4th attempt is already beyond the latency threshold (in TTI 24).

[0057] In order to increase the probability of successful reception, the second NACK may be provided with a flag S, adopting the Reactive switching scheme, to switch to blind retransmission mode (where the flag S informs the transmitter to switch to blind retransmission mode). Consequently, the MS/UE does not wait for any feedback (e.g., NACK) from the BS after the third transmission, but consecutively repeats the transmission of the data in each subframe/TTI until the latency threshold is exceeded or an ACK is received from the BS.

[0058] In doing so, the number of transmission attempts is doubled from 3 to 6 in this example. Given the fact that the probability of successful reception becomes significantly higher with each other attempt, the blind retransmission phase is an extremely rare event. Thus, the negative impact on spectral efficiency may be relatively negligible, while the probability of a service failure of the considered UE/MS is reduced by orders of magnitudes.

[0059] An example rough quantitative assessment with the trivial Automatic Repeat reQuest (ARQ) scheme: Assume Packet Error Rate 10%. Combining of packets in not exploited, e.g. each transmission attempt is an independent event. Probability of successful reception after the first transmission is 90%, after the second transmission 99% and so on. Hence in our scheme 99.9999% success rate can be achieved (6 attempts before latency threshold is violated), while in the conventional NACK-based (3 attempts) only 99.9%. Only 1% of all transactions switch to blind retransmissions, hence the impact on the resource consumption with respect to the NACK-based scheme due to the hybrid scheme is roughly two orders of magnitude less than the Blind retransmission mode.

[0060] More details are described about the performance of the different schemes in FIGs. 6 and 7, where the latency distribution and resource consumption are simulated by a single transmission simulator, with the parameters (some example parameters) described in the table below. [0061 ]

[0062] FIG. 6 is a diagram illustrating a probability mass function (PMF) of a successful transmission latency with different retransmission modes/schemes according to an example implementation. FIG. 7 is a diagram illustrating a

Cumulative Density Function (CDF) of the sum of the occupied bandwidth in all transmissions for a single packet according to an example implementation.

[0063] In FIG. 6, it can be seen that the NACK-based algorithm cannot reach the desired latency with ultra-reliability (e.g., 10^"5) with two transmissions. Since the third transmission occurs after the 1 ms with probability higher than 10^"3, the reliability target is violated. The BLIND and Hybrid scheme achieves the required URLLC performance. However, as shown in FIG. 7, the CDF of the occupied resources for such algorithms is almost the same as the efficient NACK-based and the proposed Hybrid one, while the BLIND performs poorly, with almost 300% more resource consumption. Nevertheless, the tails of such distribution in indicate a small increase of the required resources for the Hybrid scheme, that is anyway negligible if compared to the Blind scheme.

[0064] Summary of advantages: Hybrid retransmission scheme which allows for clearly improved reliability of URLLC services (or other high reliability services) without the huge impact on spectral efficiency required by blind retransmission schemes, but only when necessary.

[0065] Further embodiments for improvements of reliability in terms of reducing the residual error rate: The continuous retransmission may be combined with frequency hopping for maximizing diversity. Optionally the transmit power can be increased for the continuous retransmission part (e.g., using maximum transmit power). Optionally the amount of invested radio resources per transmission can be increased for the continuous retransmission part.

[0066] Optional usage of the scheme: The hybrid scheme can also be constructed in any other combination of blind retransmissions and NACK-based mode. In a coverage-limited situation (under difficult propagation conditions or with low transmit power capabilities), the hybrid scheme can start with a few blind retransmissions, then switch to regular NACK-based mode, then when approaching the deadline switch to use again blind retransmissions. This configuration can, e.g., be indicated by RRC configuration messages (as in (D) described above, for example).

[0067] Example 1 : FIG. 8A is a flow chart illustrating operation of a network node according to an example implementation. Operation 810 includes transmitting data from a first network node to a second network node within a wireless network. Operation 815 includes retransmitting, one or more times during a first phase, the data from the first network node to the second network node using a first retransmission mode. Operation 820 includes detecting a condition. Operation 825 includes switching, by the first network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode. And, operation 830 includes retransmitting, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode. [0068] Example 2: According to an example implementation of example 1, wherein the condition comprises a first condition, the method further comprising: detecting, by the first network node, a second condition; switching, by the first network node in response to the second detected condition, a retransmission mode from the second retransmission mode to a third retransmission mode that is different from at least the second retransmission mode; and retransmitting, one or more times during a third phase, the data from the first network node to the second network node using the third retransmission mode.

[0069] Example 3: According to an example implementation of any of examples 1-2, wherein the first retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to at least one of: receiving a NACK from the second network node and expiration of a timer at the first network node after failing to receive an acknowledgement (ACK) for the data; and the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits, until receiving an acknowledgement for the data, the data to the second network node without receiving an explicit retransmission request for the data from the second network node.

[0070] Example 4: According to an example implementation of any of examples 1-3, wherein the blind transmission mode comprises a blind transmission mode in which the first network node retransmits the data to the second network node regardless whether the first network node has received a negative acknowledgement (NACK) from the second network node for the data.

[0071 ] Example 5: According to an example implementation of any of examples 1-4, wherein the second retransmission mode comprises a blind

retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node, wherein under the blind retransmission mode the first network node continues to retransmit the data, one or more times, to the second network node until either the first network node receives an acknowledgement (ACK) for the data or a latency budget for the data has expired.

[0072] Example 6 According to an example implementation of any of examples 1-5, wherein: the first retransmission mode comprises a blind

retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node; and the second retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to receiving a NACK from the second network node.

[0073] Example 7: According to an example implementation of any of examples 1-6, and further comprising: transmitting, from the first network node to the second network node, control information indicating that the first network node has switched, will switch or is switching a retransmission mode from the first retransmission mode to the second retransmission mode.

[0074] Example 8: According to an example implementation of any of examples 1-7, wherein the detecting the condition comprises: receiving, by the first network node from the second network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode.

[0075] Example 9: According to an example implementation of any of examples 1-8, wherein the mode switch signal is received via control information based on one or more of the following: the mode switch signal is received by the first network node with a negative acknowledgement (NACK) from the second network node; and, the mode switch signal is received by the first network node with a scheduling resource allocation or scheduling grant from the second network node.

[0076] Example 10: According to an example implementation of any of examples 1-9, wherein the detecting the condition comprises: receiving, by the first network node from the second network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode, wherein the mode switch signal is received based on at least one of the following: the mode switch signal is received via a radio resource control (RRC) message; the mode switch signal is received with a hybrid automatic repeat request (HARQ) configuration information; the mode switch signal is received with a resource request, or allocation scheduling grant; the mode switch signal is piggybacked on or provided with a received negative acknowledgement (NACK) with respect to the data; and the mode switch signal is received via downlink control information (DCI). [0077] Example 11 : According to an example implementation of any of examples 1-10, and further comprising: wherein the detecting the condition comprises at least one of the following: detecting, by the first network node, that the first network node has retransmitted the data a predetermined number of times without receiving an acknowledgement (ACK) from the second network node for the data; and detecting, by the first network node, that a threshold period of time has elapsed since the transmission of the data, without receiving an acknowledgement (ACK) from the second network node for the data.

[0078] Example 12: According to an example implementation of any of examples 1-11, and further comprising: transmitting, by the first network node to the second network node, control information indicating a first number of times the first network node will retransmit the data to the second network node before switching modes; wherein the detecting the condition comprises detecting, by the first network node, that the first network node has retransmitted the data the first number of times without receiving an acknowledgement (ACK) from the second network node for the data.

[0079] Example 13: According to an example implementation of any of examples 1-12, and further comprising: transmitting, by the first network node to the second network node, control information indicating a threshold period of time the first network node will retransmit the data to the second network node before switching modes; wherein the detecting the condition comprises detecting, by the first network node, that the threshold period of time has elapsed since the transmission of the data, without receiving an acknowledgement (ACK) from the second network node for the data.

[0080] Example 14: According to an example implementation of any of examples 1-13, wherein the detecting the condition comprises at least one of the following: detecting, by the first network node, that a threshold period of time has elapsed since the transmission of the data, without receiving an acknowledgement (ACK) from the second network node for the data; and detecting, by the first network node, that the first network node has retransmitted the data a threshold number of times without receiving an acknowledgement (ACK) from the second network node for the data.

[0081 ] Example 15: According to an example implementation of any of examples 1-14, wherein the detecting the condition comprises at least one of the following: receiving, by the first network node from the second network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode in response to the second network node detecting that either a threshold period of time has elapsed since the transmission of the data or the first network node has retransmitted the data a threshold number of times without receiving an acknowledgement (ACK) from the second network node for the data.

[0082] Example 16: According to an example implementation of any of examples 1-15, wherein detecting the condition comprises: detecting a battery status or a change in battery status of the first network node.

[0083] Example 17: According to an example implementation of any of examples 1-16, wherein: the first network node comprises a user device; and the second network node comprises a base station.

[0084] Example 18: According to an example implementation of any of examples 1-17, wherein the first network node comprises a base station; and the second network node comprises a user device.

[0085] Example 19: An apparatus comprising means for performing a method of any of examples 1-18.

[0086] Example 20: An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to perform a method of any of examples 1-18.

[0087] Example 21 : An apparatus comprising a computer program product including a non-transitory computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of any of examples 1-18.

[0088] Example 22: FIG. 8B is a flow chart illustrating operation of a network node according to another example implementation. Operation 840 includes attempting to receive, by a second network node within a wireless network during a first phase, data that was retransmitted from a first network node based on a first retransmission mode. Operation 845 includes detecting a condition. Operation 850 includes switching, by the second network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode. And, operation 855 includes attempting to receive, by the second network node during a second phase, data that was retransmitted from the first network node based on the second retransmission mode.

[0089] Example 23 : According to an example implementation of example 22, and further comprising: sending, by the second network node to the first network node, a negative acknowledgement based on a failure to receive the retransmitted data.

[0090] Example 24: According to an example implementation of any of examples 22-23, wherein the condition comprises a first condition, the method further comprising: detecting, by the second network node, a second condition; switching, by the second network node in response to the second detected condition, a

retransmission mode from the second retransmission mode to a third retransmission mode that is different from at least the second retransmission mode; and attempting to receive, by the second network node during a third phase, data that was retransmitted from the first network node based on the third retransmission mode.

[0091 ] Example 25: According to an example implementation of any of examples 22-24, wherein: the first retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to at least one of: receiving a NACK from the second network node and an expiration of a timer at the first network node after failing to receive an acknowledgement (ACK) for the data; and the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving a NACK or other explicit retransmission request for the data from the second network node.

[0092] Example 26: According to an example implementation of any of examples 22-25, wherein the blind transmission mode comprises a blind transmission mode in which the first network node retransmits the data to the second network node regardless whether the first network node has received a negative acknowledgement (NACK) from the second network node for the data.

[0093] Example 27: According to an example implementation of any of examples 22-26, wherein the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node, wherein under the blind retransmission mode the first network node continues to retransmit the data, one or more times, to the second network node until either the first network node receives an acknowledgement (ACK) for the data or a latency budget for the data has expired.

[0094] Example 28: According to an example implementation of any of examples 22-27, wherein: the first retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node; and the second retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to receiving a NACK from the second network node.

[0095] Example 29: According to an example implementation of any of examples 22-28, wherein the detecting the condition comprises: receiving, by the second network node from the second network node, control information indicating that the first network node has switched, will switch or is switching a retransmission mode from the first retransmission mode to the second retransmission mode.

[0096] Example 30: According to an example implementation of any of examples 22-29 and further comprising: transmitting, by the second network node to the first network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode.

[0097] Example 31 : According to an example implementation of any of examples 22-30, wherein the mode switch signal is transmitted via control information based on one or more of the following: the mode switch signal is transmitted by the second network node with a negative acknowledgement (NACK) from the second network node; and, the mode switch signal is transmitted by the second network node with a scheduling resource allocation or scheduling grant from the second network node.

[0098] Example 32: According to an example implementation of any of examples 22-31, wherein the mode switch signal is transmitted by the second network node based on at least one of the following: the mode switch signal is transmitted via a radio resource control (RRC) message; the mode switch signal is transmitted with a hybrid automatic repeat request (HARQ) configuration information; the mode switch signal is transmitted with a resource request or scheduling grant; the mode switch signal is piggy-backed on or provided with a received negative acknowledgement (NACK) with respect to the data; and the mode switch signal is transmitted via downlink control information (DO).

[0099] Example 33: According to an example implementation of any of examples 22-32, and further comprising: receiving, by the second network node from first network node, control information indicating either a threshold period of time or a first number of times the first network node will retransmit the data to the second network node before switching modes.

[00100] Example 34: According to an example implementation of any of examples 22-33, and further comprising: wherein the detecting the condition comprises at least one of the following: detecting, by the second network node, that the first network node has retransmitted the data a predetermined number of times, without the second network node being able to receive the data; and detecting, by the second network node, that a threshold period of time has elapsed since the transmission of the data, without the second network node being able to receive the data.

[00101 ] Example 35: According to an example implementation of any of examples 22-34, wherein the detecting the condition comprises at least one of the following: detecting, by the second network node, that either a threshold period of time has elapsed since the transmission of the data or the first network node has retransmitted the data a threshold number of times; and the method further comprising: transmitting, by the second network node to the first network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode.

[00102] Example 36: According to an example implementation of any of examples 22-35, wherein detecting the condition comprises: receiving, by the second network node, a message indicating a battery status or a change in battery status of the first network node.

[00103] Example 37: According to an example implementation of any of examples 22-36, wherein: the first network node comprises a user device (UE); and the second network node comprises a base station.

[00104] Example 38: According to an example implementation of any of examples 22-37, wherein: the first network node comprises a base station; and the second network node comprises a user device. [00105] Example 39: An apparatus comprising means for performing a method of any of examples 22-38.

[00106] Example 40: An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to perform a method of any of examples 22-38.

[00107] Example 41 : An apparatus comprising a computer program product including a non-transitory computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of any of examples 22-38.

[00108] FIG. 9 is a block diagram of a wireless station (e.g., AP, BS, eNB, UE or user device) 1000 according to an example implementation. The wireless station 1000 may include, for example, one or two RF (radio frequency) or wireless transceivers 1002A, 1002B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit/entity (controller) 1004 to execute instructions or software and control transmission and receptions of signals, and a memory 1006 to store data and/or instructions.

[00109] Processor 1004 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 1004, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 1002 (1002A or 1002B). Processor 1004 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 1002, for example). Processor 1004 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1004 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and/or any combination of these. Using other terminology, processor 1004 and transceiver 1002 together may be considered as a wireless transmitter/receiver system, for example. [00110] In addition, referring to FIG. 9, a controller (or processor) 1008 may execute software and instructions, and may provide overall control for the station 1000, and may provide control for other systems not shown in FIG. 9, such as controlling input/output devices (e.g., display, keypad), and/or may execute software for one or more applications that may be provided on wireless station 1000, such as, for example, an email program, audio/video applications, a word processor, a Voice over IP application, or other application or software.

[0011 1 ] In addition, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 1004, or other controller or processor, performing one or more of the functions or tasks described above.

[00112] According to another example implementation, RF or wireless transceiver(s) 1002A/1002B may receive signals or data and/or transmit or send signals or data. Processor 1004 (and possibly transceivers 1002A/1002B) may control the RF or wireless transceiver 1002A or 1002B to receive, send, broadcast or transmit signals or data.

[00113] The embodiments are not, however, restricted to the system that is given as an example, but a person skilled in the art may apply the solution to other communication systems. Another example of a suitable communications system is the 5G concept. It is assumed that network architecture in 5G will be quite similar to that of the LTE-advanced. 5G is likely to use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[00114] It should be appreciated that future networks will most probably utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio

communications this may mean node operations may be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

[00115] Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Implementations may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Implementations may also be provided on a computer readable medium or computer readable storage medium, which may be a non-transitory medium. Implementations of the various techniques may also include implementations provided via transitory signals or media, and/or programs and/or software implementations that are downloadable via the Internet or other network(s), either wired networks and/or wireless networks. In addition, implementations may be provided via machine type communications (MTC), and also via an Internet of Things (IOT).

[00116] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal,

telecommunications signal, and software distribution package, for example.

Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

[00117] Furthermore, implementations of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating

computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers,...) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. The rise in popularity of smartphones has increased interest in the area of mobile cyber-physical systems. Therefore, various implementations of techniques described herein may be provided via one or more of these technologies.

[00118] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[00119] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC

(application-specific integrated circuit).

[00120] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry. [00121 ] To provide for interaction with a user, implementations may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a user interface, such as a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[00122] Implementations may be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation, or any combination of such back-end, middleware, or front-end components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[00123] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the various embodiments.

Claims

WHAT IS CLAIMED IS :

1. A method comprising:

transmitting data from a first network node to a second network node within a wireless network;

retransmitting, one or more times during a first phase, the data from the first network node to the second network node using a first retransmission mode;

detecting a condition;

switching, by the first network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; and

retransmitting, one or more times during a second phase, the data from the first network node to the second network node using the second retransmission mode.

2. The method of claim 1 wherein the condition comprises a first condition, the method further comprising:

detecting, by the first network node, a second condition;

switching, by the first network node in response to the second detected condition, a retransmission mode from the second retransmission mode to a third retransmission mode that is different from at least the second retransmission mode; and

retransmitting, one or more times during a third phase, the data from the first network node to the second network node using the third retransmission mode.

3. The method of any of claims 1-2 wherein:

the first retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to at least one of: receiving a NACK from the second network node and expiration of a timer at the first network node after failing to receive an acknowledgement (ACK) for the data; and

the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits, until receiving an acknowledgement for the data, the data to the second network node without receiving an explicit retransmission request for the data from the second network node.

4. The method of claim 3 wherein the blind transmission mode comprises a blind transmission mode in which the first network node retransmits the data to the second network node regardless whether the first network node has received a negative acknowledgement (NACK) from the second network node for the data.

5. The method of any of claims 1-4 wherein the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node, wherein under the blind retransmission mode the first network node continues to retransmit the data, one or more times, to the second network node until either the first network node receives an acknowledgement (ACK) for the data or a latency budget for the data has expired.

6. The method of any of claims 1-5 wherein:

the first retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node; and

the second retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to receiving a NACK from the second network node.

7. The method of any of claims 1-6 and further comprising:

transmitting, from the first network node to the second network node, control information indicating that the first network node has switched, will switch or is switching a retransmission mode from the first retransmission mode to the second retransmission mode.

8. The method of any of claims 1-7 wherein the detecting the condition comprises:

receiving, by the first network node from the second network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode.

9. The method of claim 8 wherein the mode switch signal is received via control information based on one or more of the following:

the mode switch signal is received by the first network node with a negative acknowledgement (NACK) from the second network node;

the mode switch signal is received by the first network node with a scheduling resource allocation or scheduling grant from the second network node.

10. The method of any of claims 1-9 wherein the detecting the condition comprises:

receiving, by the first network node from the second network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode, wherein the mode switch signal is received based on at least one of the following:

the mode switch signal is received via a radio resource control (RRC) message;

the mode switch signal is received with a hybrid automatic repeat request (HARQ) configuration information;

the mode switch signal is received with a resource request, or allocation scheduling grant;

the mode switch signal is piggy -backed on or provided with a received negative acknowledgement (NACK) with respect to the data; and

the mode switch signal is received via downlink control information (DCI).

11. The method of any of claims 1-10 and further comprising:

wherein the detecting the condition comprises at least one of the following: detecting, by the first network node, that the first network node has retransmitted the data a predetermined number of times without receiving an acknowledgement (ACK) from the second network node for the data; and

detecting, by the first network node, that a threshold period of time has elapsed since the transmission of the data, without receiving an acknowledgement

(ACK) from the second network node for the data.

12. The method any of claims 1-1 1 and further comprising:

transmitting, by the first network node to the second network node, control information indicating a first number of times the first network node will retransmit the data to the second network node before switching modes;

wherein the detecting the condition comprises detecting, by the first network node, that the first network node has retransmitted the data the first number of times without receiving an acknowledgement (ACK) from the second network node for the data.

13. The method of any of claims 1-12 and further comprising:

transmitting, by the first network node to the second network node, control information indicating a threshold period of time the first network node will retransmit the data to the second network node before switching modes;

wherein the detecting the condition comprises detecting, by the first network node, that the threshold period of time has elapsed since the transmission of the data, without receiving an acknowledgement (ACK) from the second network node for the data.

14. The method of any of claims 1 -13 wherein the detecting the condition comprises at least one of the following:

detecting, by the first network node, that a threshold period of time has elapsed since the transmission of the data, without receiving an acknowledgement (ACK) from the second network node for the data; and

detecting, by the first network node, that the first network node has retransmitted the data a threshold number of times without receiving an

acknowledgement (ACK) from the second network node for the data.

15. The method of any of claims 1 -14 wherein the detecting the condition comprises at least one of the following:

receiving, by the first network node from the second network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode in response to the second network node detecting that either a threshold period of time has elapsed since the transmission of the data or the first network node has retransmitted the data a threshold number of times without receiving an acknowledgement (ACK) from the second network node for the data.

16. The method of any of claims 1-15 wherein detecting the condition comprises:

detecting a battery status or a change in battery status of the first network node.

17. The method of any of claims 1 -16 wherein:

the first network node comprises a user device; and

the second network node comprises a base station.

18. The method of any of claims 1 -16 wherein:

the first network node comprises a base station; and

the second network node comprises a user device.

19. An apparatus comprising means for performing a method of any of claims 1 -18.

20. An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to perform a method of any of claims 1 -18.

21. An apparatus comprising a computer program product including a non- transitory computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of any of claims 1-18.

22. A method comprising:

attempting to receive, by a second network node within a wireless network during a first phase, data that was retransmitted from a first network node based on a first retransmission mode;

detecting a condition;

switching, by the second network node in response to the detected condition, a retransmission mode from the first retransmission mode to a second retransmission mode that is different from the first retransmission mode; and

attempting to receive, by the second network node during a second phase, data that was retransmitted from the first network node based on the second retransmission mode.

23. The method of claim 22 and further comprising:

sending, by the second network node to the first network node, a negative acknowledgement based on a failure to receive the retransmitted data.

24. The method of any of claims 22-23 wherein the condition comprises a first condition, the method further comprising:

detecting, by the second network node, a second condition;

switching, by the second network node in response to the second detected condition, a retransmission mode from the second retransmission mode to a third retransmission mode that is different from at least the second retransmission mode; and

attempting to receive, by the second network node during a third phase, data that was retransmitted from the first network node based on the third retransmission mode.

25. The method of any of claims 22-24 wherein:

the first retransmission mode comprises a negative acknowledgement (NACK)-based retransmission mode in which the first network node retransmits the data to the second network node in response to at least one of: receiving a NACK from the second network node and an expiration of a timer at the first network node after failing to receive an acknowledgement (ACK) for the data; and the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving a NACK or other explicit retransmission request for the data from the second network node.

26. The method of claim 25 wherein the blind transmission mode comprises a blind transmission mode in which the first network node retransmits the data to the second network node regardless whether the first network node has received a negative acknowledgement (NACK) from the second network node for the data.

27. The method of any of claims 22-26 wherein the second retransmission mode comprises a blind retransmission mode in which the first network node retransmits the data to the second network node without receiving an explicit retransmission request for the data from the second network node, wherein under the blind retransmission mode the first network node continues to retransmit the data, one or more times, to the second network node until either the first network node receives an acknowledgement (ACK) for the data or a latency budget for the data has expired.

28. The method of any of claims 22-27 wherein:

29. The method of any of claims 22-28 wherein the detecting the condition comprises:

receiving, by the second network node from the second network node, control information indicating that the first network node has switched, will switch or is switching a retransmission mode from the first retransmission mode to the second retransmission mode.

30. The method of any of claims 22-29 and further comprising:

transmitting, by the second network node to the first network node, a mode switch signal instructing the first network node to switch from the first retransmission mode to the second retransmission mode.

31. The method claim 30 wherein the mode switch signal is transmitted via control information based on one or more of the following:

the mode switch signal is transmitted by the second network node with a negative acknowledgement (NACK) from the second network node;

the mode switch signal is transmitted by the second network node with a scheduling resource allocation or scheduling grant from the second network node.

32. The method of claim 30 wherein the mode switch signal is transmitted by the second network node based on at least one of the following:

the mode switch signal is transmitted via a radio resource control (RRC) message;

the mode switch signal is transmitted with a hybrid automatic repeat request (HARQ) configuration information;

the mode switch signal is transmitted with a resource request or scheduling grant;

the mode switch signal is piggy-backed on or provided with a received negative acknowledgement (NACK) with respect to the data; and

the mode switch signal is transmitted via downlink control information (DO).

33. The method of any of claims 22-32 and further comprising:

receiving, by the second network node from first network node, control information indicating either a threshold period of time or a first number of times the first network node will retransmit the data to the second network node before switching modes.

34. The method of any of claims 22-33 and further comprising:

wherein the detecting the condition comprises at least one of the following: detecting, by the second network node, that the first network node has retransmitted the data a predetermined number of times, without the second network node being able to receive the data; and

detecting, by the second network node, that a threshold period of time has elapsed since the transmission of the data, without the second network node being able to receive the data.

35. The method of any of claims 22-34 wherein the detecting the condition comprises at least one of the following: detecting, by the second network node, that either a threshold period of time has elapsed since the transmission of the data or the first network node has retransmitted the data a threshold number of times; and the method further comprising:

36. The method of any of claims 22-35 wherein detecting the condition comprises:

receiving, by the second network node, a message indicating a battery status or a change in battery status of the first network node.

37. The method of any of claims 22-36 wherein:

the first network node comprises a user device; and

the second network node comprises a base station.

38. The method of any of claims 22-36 wherein:

the first network node comprises a base station; and

the second network node comprises a user device.

39. An apparatus comprising means for performing a method of any of claims

22-38.

40. An apparatus comprising at least one processor and at least one memory including computer instructions that, when executed by the at least one processor, cause the apparatus to perform a method of any of claims 22-38.

41. An apparatus comprising a computer program product including a non- transitory computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of any of claims 22-38.