WO2018024946A1

WO2018024946A1 - Blind retransmissions over shared resources

Info

Publication number: WO2018024946A1
Application number: PCT/FI2017/050562
Authority: WO
Inventors: Renato ABREU; Gilberto BERARDINELLI; Preben Mogensen; Klaus Pedersen
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2016-08-05
Filing date: 2017-08-02
Publication date: 2018-02-08
Anticipated expiration: 2019-02-05

Abstract

Various communication systems may benefit from the appropriate handling of transmissions. For example, certain wireless systems may benefit from the suitable handling of blind retransmissions over shared resources. A method can include providing a dedicated channel for a user equipment for initial uplink transmission of a message by the user equipment. The method can also include providing a shared channel for the user equipment for blind retransmissions of the message.

Description

TITLE:

Blind Retransmissions over Shared Resources

BACKGROUND:

5 Field:

Various communication systems may benefit from the appropriate handling of transmissions. For example, certain wireless systems may benefit from the suitable handling of blind retransmissions over shared resources. l o Description of the Related Art:

The advent of machine type communications (MTC) applications in cellular networks brings new challenges due to specific characteristics of these systems, such as different delay and reliability tolerances and sometimes unpredictable small data transmissions. The traditional resource scheduling and retransmission procedure, as currently applied in long term evolution (LTE) 15 networks, may not be suitable for mission critical MTC due to the time consumption and error proneness of the multiple messages being exchanged between nodes.

Even if a dynamic based scheduling were able to perform a grant for the initial transmission in time, in case a retransmission is necessary, the round trip time for the feedback signaling would 20 increase the tail of the latency distribution. That is, the process of acknowledgments and retransmission granting can cause extended delays, which may be undesirable for ultra-reliable low latency communication (URLLC) use cases. Besides that, errors can occur either on acknowledge decoding or in retransmission signaling, affecting the reliability of system.

25 Pre-scheduling resources conservatively for robust transmissions can reduce the signaling overhead and delays caused by the request/grant procedure, while achieving reliability and latency requirements associated with URLLC. However, such a procedure can easily drain the capacity of the network. Besides that, the pre-scheduling allocation for unpredictable data traffic could result in waste of radio resources when there is no data available for transmission. In a typical

30 scenario, a UE/device operating in semi-persistent scheduling mode may occupy the assigned resource from a radio perspective, no matter whether the resource is used for data transmission or not. Contention based access schemes, in which the resources are not UE-specific but allocated to a group of UEs, combined with semi-persistent allocation, can give opportunity for the UEs to transmit sporadic data over the shared resources with reduced request/grant signaling (and reduced associated overhead). However, collisions may happen if more than one UE uses the shared resource at the same instant, which can result in failures for decoding the transmitted block of data. In a dense and/or highly loaded network, such a situation may happen often, causing a high block error rate (BLER) and hence an increased overall latency in the network due to large amount of retransmissions. Therefore, the collisions can increase BLER, retransmission signaling, average latency, and compromise the overall reliability of the system.

In fifth generation (5G) systems, MTC may exploit the usage of blind retransmissions in a proactive way, in order to increase the success probability of transmitting a message with low delay penalty. Instead of transmitting and waiting for the feedback to retransmit, the node may just aggressively retransmit for a predetermined number of attempts or until a positive acknowledgement is received. However, this method can also lead to poor resource utilization, since further retransmissions might not be needed if the message was already detected on the initial transmissions.

BRIEF DESCRIPTION OF THE DRAWINGS:

For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

Figure 1 illustrates a method according to certain embodiments.

Figure 2 illustrates resource allocation according to certain embodiments.

Figure 3 illustrates an example of downlink transmission according to certain embodiments. Figure 4 illustrates using semi-persistent uplink allocation for different UEs, according to certain embodiments.

Figure 5 illustrates an access node method according to certain embodiments.

Figure 6 illustrates a trend plot of resolved packet using various approaches.

Figure 7 illustrates a receiver method according to certain embodiments.

Figure 8 illustrates a method according to certain embodiments.

Figure 9 illustrates a system according to certain embodiments. DETAILED DESCRIPTION:

Certain embodiments relate to a 5G new radio (NR) architecture, with focus on ultra-reliable and low latency communication (URLLC) use cases. For example, certain embodiments may help a system meet stringent latency and reliability requirements, such as 1-10^"5 within 1ms, and average user plane latency of 0.5ms. Moreover, certain embodiments may meet these requirements in an efficient way, without draining network capacity. For example, certain embodiments may provide a procedure to perform blind retransmissions on shared radio resources together with the application of successive interference cancelation to detect remaining non-decoded data with a low delay penalty.

Retransmissions may be beneficial to improve reliability, but conventionally the problem is either node, for example a user equipment (UE), performs blind retransmission on dedicated resources, which drains channel capacity, or a delay penalty is incurred due to the round trip time for the ACK/NACK before performing a retransmission.

Certain embodiments provide an approach that permits the nodes to perform blind retransmissions with low delay penalty and improved resource utilization. More specifically, certain embodiments provide a scheme to perform efficient transmission for URLLC. Initial transmissions can be scheduled on safer resources, while automatic blind retransmissions can be configured on shared resources. The automatic blind retransmissions can be decoded by eventually relying on a successive interference cancelation receiver.

Certain embodiments can be summarized as follows, for example for an uplink transmission. Figure 1 illustrates a method according to certain embodiments.

As shown in Figure 1, at 110, a base station (BS) such as a next generation Node B (gNB) can configure semi-persistent or dynamically granted resources for a UE's initial UL transmission, for each of a plurality of UEs. The initial transmission may have a low block error rate (BLER) target, for example 10^"2, even though this BLER target may be higher than a final error probability, for example 10^"5.

At 120, the BS can also configure the UEs to perform blind retransmissions on shared retransmission channels. The retransmission channels can be shared by multiple UEs with similar traffic characteristics. The configuration can define a certain number K of blind retransmissions. Alternatively, the configuration can be defined such that retransmissions occur until the message is acknowledged. There can a maximum number of blind retransmissions even in this case.

At 130, the UE can perform the initial transmission in a dedicated channel and, at 140, can perform blind retransmissions on a shared channel. These transmissions and retransmissions can be according to the configuration from 110 and 120. Retransmissions can possibly perform frequency hopping among different shared retransmission channels to harvest diversity gain.

At 150, the BS can try to decode the initial transmissions from the UEs in their dedicated resources. At 155, the BS can store the decoded signals. Then, at 160, the BS can attempt decoding the shared channel by subtracting the already decoded signals from the combined received signal. The BS can also store signals decoded from the retransmissions.

Since the initial transmission occurs in safer resources, most of them may be decoded early. The remaining decoding may therefore be faster. The successive interference cancellation (SIC) can resolve with fewer iterations because most of the signals in the shared resources may be already successfully decoded and reconstructed such that it can be subtracted.

Thus, certain embodiments can provide a method for scheduling and combining initial transmission on protected resources with automatic blind retransmissions on a set of shared resources. Moreover, certain embodiments can provide a procedure for fast decoded retransmissions carried on shared resources using known information from previously decoded transmissions.

The following discussion provides illustration of corresponding UE and BS behaviors. The following discussion also provides corresponding air interface signaling between those entities. These are simply example illustrations of certain embodiments.

The BS can configure the UE to perform the UE's initial transmissions on safer or dedicated time- frequency resources. The BS can perform dynamic allocation for the initial transmission. Alternatively, in order to reduce signaling, the BS can use a robust radio resource control (RRC) message to configure the resources to occur periodically, as in semi-persistent scheduling. At the same time, the BS can also configure the UE to perform automatic blind retransmissions on certain shared channels. From the UE's perspective, it may be transparent whether the UE is transmitting on a shared resource or not. The BS can also assign reference signals to the UEs to be able to detect each UE's transmissions and estimate the channel.

The number of shared channels and number of consecutive retransmissions can be flexibly set. The BS can define and assign them according the load of the network and quality of service (QoS) requirements. In one possible implementation, the BS can configure the UE to retransmit until the UE receives feedback to stop, which may be a more controlled solution with the price of more signaling. Another possibility is to configure the UE to retransmit a fixed amount of repetitions, reducing the dependency of feedback signaling. The UE can also be configured to drop the packet retransmission if a certain time deadline is reached. The BS could possibly assign more than one parallel shared retransmission channel for the UE, that is, a shared resource pool for retransmissions. In this case the UE could, for instance, select randomly how many and/or which of the shared resources to use for retransmission. Retransmissions can perform frequency hopping to improve diversity or for other reasons, such as load balancing or fairness. An identifier (ID) or a preamble can be used to identify each retransmission. Alternatively, the BS and the UE can agree on a seed for a pseudo-random sequence that can determine which resources from the pool will be used.

The modulation and coding scheme (MCS) for the initial transmission can be set to achieve a relatively low BLER target, such as 10^"2, even though it is not necessarily as low as the final error probability, such as 10^"5. The retransmissions can possibly use the same MCS, and can rely on soft combining gain to improve the chances of correct detection.

For a semi-persistent configuration, in the uplink case, the UE may be able to regularly use the UE's pre-scheduled resources whenever the UE has data available for transmission, reducing control overhead, latency and error probability on control signaling. The UE can transmit the UE's available data on the initial protected resources and can then perform blind retransmission on the shared resources. The retransmissions can be simple repetitions of the same packet or can be different redundant versions of the same packet.

Figure 2 illustrates resource allocation according to certain embodiments. Figure 2 shows one example related to scheduling and transmission procedures. Thus, Figure 2 is a simple illustration of one possible realization. The time- frequency position of the resources might not necessarily be aligned as shown. In this simplified example, seven UEs can perform their initial transmission in dedicated resources. For the sake of visual simplicity and without loss of generality, such transmissions can be assumed to happen simultaneously over different frequency resources. Further, all the UEs can be allocated a set of shared resources. In case the receiver was not able to decode UE2 and UE3 on the initial transmission (BLER > 10%), for the second transmission (first retransmission) the signals from UE5 and UE6 decoded on initial transmission can be cancelled from the signal of UE3. Combined with the initial transmission the signal of UE3 can be successfully decoded. At the end, the same can happen with UE2 on the next retransmission. In this case, the non-decoded transmissions may happen on different shared retransmission resources, sorted by the UEs. The number of shared channels can decrease with the time to reduce resource utilization. The UEs may have similar traffic characteristics, such as all being MTC devices. Thus, it may be possible to have the joint transmission on the same resources.

Another embodiment can apply similar techniques also for downlink communication. Figure 3 illustrates an example of downlink transmission according to certain embodiments. The BS can transmit different packets to the same UE. This can be done using shared blind retransmission on downlink.

As shown in Figure 3, initially a BS can transmit datal in a dedicated resource. Then, datal can be retransmitted on a previously configured shared retransmission channel. Another packet, data2, can arrive for the same UE. This second packet can also initially be transmitted in a dedicated resource. After that, data2 can also be retransmitted in the shared retransmission channel combined with datal, for example dataC = datal + data2. The combined transmission could be performed as GF(2) addition or a signal superposition. Assuming that there is a high probability that datal or data2 is decoded on the initial transmission, the UE could cancel the decoded one from dataC and decode the other one. In the worst case, none of them are initially decoded and the receiver would count only with a soft combining gain to try to decode during the retransmissions. Figure 4 illustrates using semi-persistent uplink allocation for different UEs, according to certain embodiments. More particularly, Figure 4 shows another example using semi-persistent uplink allocation for different UEs and two parallel shared retransmission channels. In this particular example, there may be a transmission time interval (TTI) of 125 μβ, so there may be a semi-persistent scheduling (SPS) interval of 3 TTIs to keep the average latency of 0.5 ms for URLLC.

In Figure 4, side (a) shows resource scheduling from a base station perspective, while side (b) shows resource scheduling from a UE4 perspective. Taking UE4 for example, if the device has data to transmit, it transmits in its periodic resource and, in this example, performs two blind retransmissions on a randomly selected shared retransmission channel. If the UE4 message is not decoded from the initial transmission, the BS may be able to remove the interference from other detected UEs on the shared resource and finally decode UE4. The BS can balance the amount of scheduled resources and the number of UEs sharing the retransmission channels in order to achieve a required decoding performance.

Figure 5 illustrates an access node method according to certain embodiments. Figure 5 illustrates a procedure on the BS side that may be applied for each admitted UE for UL transmissions. The BS can perform an iterative decoding process until each transmission is resolved, or the BS can initially configure the UE to drop the packet if a certain latency deadline cannot be reached anymore.

As shown in Figure 5, at 1 the BS can connect a new URLLC UE. Then, at 2, the BS can configure the UE to use pre-defined/periodic dedicated resources for initial transmission. The BS can also, at 3, configure the UE to use a pre-defined shared resource pool for up to T blind retransmissions. Although 2 and 3 are shown in this order, the order could be reversed or the two could be done at essentially the same time, using the same message. Likewise, at 4 the BS can configure the UE to either stop transmitting after K retransmissions or stop if an acknowledgment (ACK) is received.

At 5, the BS can receive a next UE transmission on a dedicated resource and can try to decode the transmission. At 6, a determination can be made as to whether the transmission is decoded. If so, at 13 an acknowledgment of the decoded transmission can be provided. Otherwise, at 7, a determination can be made as to whether the UE can do another retransmission. If not, then the BS can simply wait for the next received transmission at 5. Otherwise, at 8, the BS can receive the next transmission on a shared resource.

At 9, the BS can identify the UE(s) transmitting on the shared resource. The BS can also, at 10, reconstruct and subtract signals of decoded UEs from the shared resources. Then, at 11, the BS can combine the signal of the UE with the UE's previous transmissions and attempt to decode. If the transmission is not decoded, the method can retum to step 7. Otherwise, the if the transmission is decoded, an acknowledgment of the decoded transmission can be provided at 13.

The received signal on the shared resource can be the combination of the transmissions from all the UEs retransmitting on that channel, considering also the channel effect over each transmission. The following equation can describe the received signal y from N UEs transmitting their signal x_t on a particular shared resource: y = h * x₁ + h₂ * x₂ + h₃ * x₃ +— h h_N * x_N + n_k =

where n_k denotes the noise power.

So, the receiver may be able to estimate the UEs channels h_t (by using configured reference symbols for instance) and may be able to reconstruct the signal from the previously decoded ones. After that, the receiver can cancel interference over the non-decoded signals. That can be part of the SIC decoding process. Ideally, each successfully decoded replica may permit removal of its interference on the other replicas, at each retransmission.

According to certain embodiments, by assigning safer resources for the initial transmission, there is a higher probability, based on the configuration provided by the BS, that most of the users are decoded in the beginning. Therefore, the successive decoding process on the shared channel can quickly resolve the remaining non-decoded transmissions.

Figure 6 illustrates a trend plot of resolved packet using various approaches. In particular, Figure 6 illustrates a trend plot for the overall number of resolved transmissions over time when comparing a proposed solution according to certain embodiments and a non-scheduled access approach. These are illustrations of simulation results for loaded scenarios.

Figure 7 illustrates a receiver method according to certain embodiments. As shown in Figure 7, a method can include, at 1 , receiving an initial transmission on a safer resource, such as a dedicated channel. At 2, the receiver can estimate and store decoded transmissions. Then, at 3, the receiver can determine whether the entire transmission is decoded. If so, then at 6 the method can end. Otherwise, at 4, the receiver can receive a shared resource with joint blind retransmissions. The receiver can then, at 5, cancel interference caused by the decoded signals against the un-decoded signals. Then, once again at 2, the receiver can estimate and store any further decoded transmissions. This process can continue to cycle through multiple repetitions of retransmission.

Figure 8 illustrates a method according to certain embodiments. The method can include, at 810, providing a dedicated channel for a user equipment for initial uplink transmission of a message by the user equipment. The method can also include, at 820, providing a shared channel for the user equipment for blind retransmissions of the message.

The method can further include, at 830, attempting to decode the initial uplink transmission received on the dedicated channel. The method can further include, at 840, attempting to decode the blind retransmissions on the shared channel. The attempting to decode the blind retransmissions can include, at 845, subtracting already decoded signals from a combined received signal.

The providing the dedicated channel, at 810, can include configuring a user equipment with semi-persistent or dynamically granted resources. Likewise, the providing the shared channel, at 820, can include providing a set of shared retransmission channels. The providing the shared channel, at 820, can include configuring the user equipment to perform an identified number of blind retransmissions. Additionally, the providing the shared channel, at 820, can include grouping the user equipment with a plurality of other user equipment based on at least one traffic characteristic. For example, various MTC devices can be grouped together because they are MTC devices. The providing the shared channel, at 820, can include configuring the user equipment to perform blind retransmissions until the message is acknowledged. A maximum number of retransmissions or a maximum duration can be configured in case the acknowledgment takes too long or never comes. The above-described features of Figure 8 can be performed by an access node, such as a base station or gNB. The following features can be performed by another device, such as a user equipment.

For example, the method can include, at 850, receiving a configuration of a dedicated channel for a user equipment for initial uplink transmission of a message by the user equipment. This can be the same configuration provided at 810. The method can also include, at 860, receiving a configuration of a shared channel for the user equipment for blind retransmissions of the message. This can be the same configuration provided at 820.

The method can further include, at 870, performing an initial uplink transmission of the message using the dedicated channel. This can be the same transmission on which a decoding attempt is made at 830. The method can also include, at 880, performing blind retransmission of the message using the shared channel. The blind retransmission at 880 can include performing frequency hopping among different shared retransmission channels.

The receiving the configuration of the dedicated channel, at 850, can include receiving a configuration of semi-persistent or dynamically granted resources. Likewise, the receiving the configuration of the shared channel, at 860, can include receiving a configuration of a set of shared retransmission channels. The receiving the configuration of the shared channel, at 860, can include receiving a configuration to perform an identified number of blind retransmissions. The receiving the configuration of the shared channel, at 870, can include receiving a configuration to perform blind retransmissions until the message is acknowledged. As mentioned above, this can explicitly or implicitly configure a maximum number of retransmissions or a maximum retransmission duration.

In certain embodiments, the initial transmissions are carried on safer resources. Thus, most of the packets may tend to be decoded in a short time. The remaining non-decoded packets can be left to be resolved during the blind retransmissions. On the other hand, for usual contention based solutions, the risk of collision after the first transmission attempt increases the overall delay for decoding the packets in loaded scenarios. Thus, certain embodiments may have various benefits and/or advantages. For example, certain embodiments may provide reduced BLER and a low delay penalty with aggressive retransmissions. Additionally, certain embodiments may provide reduced susceptibility to signaling issues to perform the retransmissions. Furthermore, certain embodiments may provide improved resource utilization scheduling the retransmissions in shared resources and doing SIC.

The receiver node may need to keep track of the signals that were already decoded to be able to perform the interference cancelation during the successive retransmissions. Additionally, the transmitting node may need to keep retransmitting until it receives an ACK or until a max number of transmissions is reached. In scenarios where the data traffic load is not high, there may be less benefit as contrasted with contention based solutions. Thus, certain embodiments may be particularly useful in cases that require ultra-reliable and low latency communication, for example in 5G. Figure 9 illustrates a system according to certain embodiments of the invention. It should be understood that each block of the flowchart of Figures 1, 5, and 8 may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry. In one embodiment, a system may include several devices, such as, for example, network element 910 and user equipment (UE) or user device 920. The system may include more than one UE 920 and more than one network element 910, although only one of each is shown for the purposes of illustration. A network element can be an access point, a base station, an eNode B (eNB), or any other network element, such as a PCell base station or a PSCell base station. Each of these devices may include at least one processor or control unit or module, respectively indicated as 914 and 924. At least one memory may be provided in each device, and indicated as 915 and 925, respectively. The memory may include computer program instructions or computer code contained therein, for example for carrying out the embodiments described above. One or more transceiver 916 and 926 may be provided, and each device may also include an antenna, respectively illustrated as 917 and 927. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided. For example, network element 910 and UE 920 may be additionally configured for wired communication, in addition to wireless communication, and in such a case antennas 917 and 927 may illustrate any form of communication hardware, without being limited to merely an antenna.

Transceivers 916 and 926 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself, but in a mast, for example. It should also be appreciated that according to the "liquid" or flexible radio concept, the operations and functionalities may be performed in different entities, such as nodes, hosts or servers, in a flexible manner. In other words, division of labor may vary case by case. One possible use is to make a network element to deliver local content. One or more functionalities may also be implemented as a virtual application that is provided as software that can run on a server.

A user device or user equipment 920 may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device, a computer, such as a tablet, provided with wireless communication capabilities, personal data or digital assistant (PDA) provided with wireless communication capabilities, vehicle, portable media player, digital camera, pocket video camera, navigation unit provided with wireless communication capabilities or any combinations thereof. The user device or user equipment 920 may be a sensor or smart meter, or other device that may usually be configured for a single location.

In an exemplifying embodiment, an apparatus, such as a node or user device, may include means for carrying out embodiments described above in relation to Figures 1, 5, and 8. Processors 914 and 924 may be embodied by any computational or data processing device, such as a central processing unit (CPU), digital signal processor (DSP), application specific integrated circuit (ASIC), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), digitally enhanced circuits, or comparable device or a combination thereof. The processors may be implemented as a single controller, or a plurality of controllers or processors. Additionally, the processors may be implemented as a pool of processors in a local configuration, in a cloud configuration, or in a combination thereof. The term circuitry may refer to one or more electric or electronic circuits. The term processor may refer to circuitry, such as logic circuitry, that responds to and processes instructions that drive a computer.

For firmware or software, the implementation may include modules or units of at least one chip set (e.g., procedures, functions, and so on). Memories 915 and 925 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate therefrom. Furthermore, the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof, such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable. The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as network element 910 and/or UE 920, to perform any of the processes described above (see, for example, Figures 1, 5, and 8). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine, applet or macro) that, when executed in hardware, may perform a process such as one of the processes described herein. Computer programs may be coded by a programming language, which may be a high-level programming language, such as objective- C, C, C++, C#, Java, etc., or a low-level programming language, such as a machine language, or assembler. Alternatively, certain embodiments of the invention may be performed entirely in hardware.

Furthermore, although Figure 9 illustrates a system including a network element 910 and a UE 920, embodiments of the invention may be applicable to other configurations, and configurations involving additional elements, as illustrated and discussed herein. For example, multiple user equipment devices and multiple network elements may be present, or other nodes providing similar functionality, such as nodes that combine the functionality of a user equipment and an access point, such as a relay node. One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention.

List of Abbreviations

3 GPP 3rd generation partnership project

5G Fifth Generation cellular technology

ACK Acknowledgement

NACK Negative-acknowledgement

BLER Block error rate

BS Base station

CB Contention based

DL Downlink

UL Uplink

eNB Evolved Node B, base station node in LTE

HARQ Hybrid automatic repeat request

LTE Long term evolution

MCS Modulation and coding scheme

MTC Mission type communication

MUD Multi-user detection

PUSCH Physical uplink shared channel

QoS Quality of Service

RRC Radio Resource Control

SIC Successive interference cancelation

SPS Semi-persistent scheduling

TTI Transmission time interval

UE User equipment

URLLC Ultra-reliable and low latency communication

VoIP Voice over IP According to a first embodiment, a method can include providing a dedicated channel for a user equipment for initial uplink transmission of a message by the user equipment. The method can also include providing a shared channel for the user equipment for blind retransmissions of the message.

In a variant, the method can further include attempting to decode the initial uplink transmission received on the dedicated channel.

In a variant, the method can further include attempting to decode the blind retransmissions on the shared channel.

In a variant, the attempting to decode the blind retransmissions can include subtracting already decoded signals from a combined received signal. In a variant, the providing the dedicated channel can include configuring a user equipment with semi-persistent or dynamically granted resources.

In a variant, the providing the shared channel can include providing a set of shared retransmission channels.

In a variant, the providing the shared channel can include configuring the user equipment to perform an identified number of blind retransmissions.

In a variant, the providing the shared channel can include grouping the user equipment with a plurality of other user equipment based on at least one traffic characteristic.

In a variant, the providing the shared channel can include configuring the user equipment to perform blind retransmissions until the message is acknowledged. According to a second embodiment, a method can include receiving a configuration of a dedicated channel for a user equipment for initial uplink transmission of a message by the user equipment. The method can also include receiving a configuration of a shared channel for the user equipment for blind retransmissions of the message. In a variant, the method can further include performing an initial uplink transmission of the message using the dedicated channel. In a variant, the method can further include performing blind retransmission of the message using the shared channel.

In a variant, the blind retransmission can include performing frequency hopping among different shared retransmission channels.

In a variant, the receiving the configuration of the dedicated channel can include receiving a configuration of semi-persistent or dynamically granted resources.

In a variant, the receiving the configuration of the shared channel can include receiving a configuration of a set of shared retransmission channels.

In a variant, the receiving the configuration of the shared channel can include receiving a configuration to perform an identified number of blind retransmissions. In a variant, the receiving the configuration of the shared channel can include receiving a configuration to perform blind retransmissions until the message is acknowledged.

According to third and fourth embodiments, an apparatus can include means for performing the method according to the first and second embodiments respectively, in any of their variants.

According to fifth and sixth embodiments, an apparatus can include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus at least to perform the method according to the first and second embodiments respectively, in any of their variants.

According to seventh and eighth embodiments, a computer program product may encode instructions for performing a process including the method according to the first and second embodiments respectively, in any of their variants.

According to ninth and tenth embodiments, a non-transitory computer readable medium may encode instructions that, when executed in hardware, perform a process including the method according to the first and second embodiments respectively, in any of their variants.

According to eleventh and twelfth embodiments, a system may include at least one apparatus according to the third or fifth embodiments in communication with at least one apparatus according to the fourth or sixth embodiments, respectively in any of their variants.

Claims

CLAIMS:

1. A method comprising:

configuring user equipment to use a dedicated resource for an initial transmission and to use a shared resource pool for blind retransmissions;

receiving the initial transmission on the dedicated resource and attempting to decode the initial transmission;

if the initial transmission is decoded, providing an acknowledgment to the user equipment; if the initial transmission is not decoded, receiving at least one blind retransmission on a shared resource taken from the shared resource pool and identifying the transmitting user equipment, and

combining the initial transmission and the at least one blind retransmission and attempting to decode the combined transmission, if a combined transmission is decoded, providing an acknowledgment to the user equipment.

2. The method of claim 1, wherein the configuring the shared resource pool further comprises:

configuring the user equipment to perform an identified number of blind retransmissions or

configuring the user equipment to perform blind retransmissions until the acknowledgment is received.

3. The method of claim 1 or 2, further comprising, if the at least one blind retransmission is not acknowledged,

receiving at least one second blind retransmission on a shared resource taken from the shared resource pool and identifying the transmitting user equipment, and

combining the initial transmission, the at least one blind retransmission and the at least one second blind retransmission and attempting to decode a combined transmission, if the combined transmission is decoded, providing an acknowledgment to the user equipment.

4. The method of any preceding claim, further comprising:

if the initial transmission or the at least one blind retransmission is not decoded, removing interference caused by other detected user equipment on the shared resource for decoding the at least one blind retransmission and/or the at least one second blind retransmission.

5. The method of any preceding claim, wherein the attempting to decode the at least one blind retransmission further comprises: subtracting the decoded initial transmission from the combination of the initial transmission and the at least one blind retransmission and/or wherein the attempting to decode the at least one second blind retransmission further comprises: subtracting the decoded initial transmission and the at least one blind retransmission from the combination of the initial transmission, the at least one blind retransmission and the at least one second blind retransmission.

6. An apparatus comprising at least one processor and at least one memory including a computer program code configured to, with the at least one processor, cause the apparatus at least to perform:

configure user equipment to use a dedicated resource for an initial transmission and to use a shared resource pool for blind retransmissions;

receive the initial transmission on the dedicated resource and attempt to decode the initial transmission;

if the initial transmission is decoded, provide an acknowledgment to the user equipment; if the initial transmission is not decoded, receive at least one blind retransmission on a shared resource taken from the shared resource pool and identify the transmitting user equipment, and

combine the initial transmission and the at least one blind retransmission and attempt to decode the combined transmission, if a combined transmission is decoded, provide an acknowledgment to the user equipment.

7. The apparatus of claim 6, wherein the configuring the shared resource pool further comprises:

configure the user equipment to perform an identified number of blind retransmissions or configure the user equipment to perform blind retransmissions until the acknowledgment is received.

8. The apparatus of claim 6 or 7, further comprising, if the at least one blind retransmission is not acknowledged,

receive at least one second blind retransmission on a shared resource taken from the shared resource pool and identify the transmitting user equipment, and

combine the initial transmission, the at least one blind retransmission and the at least one second blind retransmission and attempt to decode a combined transmission, if the combined transmission is decoded, provide an acknowledgment to the user equipment.

9. The apparatus of any preceding claim 6 to 8, further comprising:

if the initial transmission or the at least one blind retransmission is not decoded, remove interference caused by other detected user equipment on the

shared resource for decoding the at least one blind retransmission and/or the at least one second blind retransmission.

10. The apparatus of any preceding claim 6 to 9, wherein the attempting to decode the at least one blind retransmission further comprises: subtract the decoded initial transmission from the combination of the initial transmission and the at least one blind retransmission and/or wherein the attempt to decode the at least one second blind retransmission further comprises: subtract the decoded initial transmission and the at least one blind retransmission from the combination of the initial transmission, the at least one blind retransmission and the at least one second blind retransmission.

11. A non-transitory computer readable medium storing a program causing a computer to execute a process, the process comprising:

causing receiving the initial transmission on the dedicated resource and attempting to decode the initial transmission;

if the initial transmission is decoded, providing an acknowledgment to the user equipment; if the initial transmission is not decoded, causing receiving at least one blind retransmission on a shared resource taken from the shared resource pool and identifying the transmitting user equipment, and

12. A computer program comprising instructions which, when the program is executed by a computer, cause an apparatus to carry out the method of any of claims 1 to 5.