CN112272956A - Transmission resource sharing - Google Patents

Abstract

A method of providing fair access to shared transmission resources among a plurality of devices is disclosed. A group of devices belonging to a group selects a common value for the contention window size to fairly contend for transmission resources with other, non-associated devices.

Description

Transmission resource sharing

Technical Field

The present disclosure relates to sharing transmission resources in cellular wireless networks, and in particular to sharing unlicensed transmission resources between cellular devices and other devices.

Background

Wireless communication systems, such as the third-generation (3G) mobile telephone standards and technologies, are well known. Such 3G standards and technologies were developed by the Third Generation Partnership Project (3 GPP). Third generation wireless communications have generally been developed to support macrocell mobile telephone communications. Communication systems and networks have evolved towards broadband and mobile systems.

In a cellular Radio communication system, a User Equipment (UE) is connected to a Radio Access Network (RAN) via a Radio link. The RAN comprises a set of base stations that provide radio links to UEs located in cells covered by the base stations, and an interface to a Core Network (CN) that provides full Network control. It will be appreciated that the RAN and CN each perform respective network-wide related functions. For convenience, the term cellular network will be used to refer to the combined RAN & CN and it should be understood that this term is used to refer to the various systems for performing the disclosed functionality.

The 3GPP has developed a so-called Long Term Evolution (LTE) system, i.e. an Evolved Universal Mobile telecommunications system terrestrial Radio Access Network (E-UTRAN) for Mobile Access networks, in which one or more macro cells are supported by base stations called enodebs or enbs (Evolved nodebs). Recently, LTE is being developed further towards so-called 5G or New Radio (NR) systems, where one or more cells are supported by a base station called a gNB. NR is proposed to use an Orthogonal Frequency Division Multiplexing (OFDM) physical transmission format.

The NR protocol is intended to provide an option to operate in an unlicensed radio band, called NR-U. When operating in the unlicensed radio band, the gNB and the UE must contend with other devices for physical medium/resource access. For example, Wi-Fi, NR-U, and Licensed Assisted Access (LAA) may use the same physical resources.

To share resources, a device (e.g., a gNB or UE) may monitor available resources and only begin transmitting when there is no conflict with another device that is already using the resources. This is called Clear Channel Assessment (CCA). This is typically performed using a Listen Before Talk (LBT) protocol, where a device "listens" for transmissions on resources for a period of time to determine whether other devices are transmitting on those resources. If no transmissions are detected that exceed any applicable threshold, the LBT procedure is successful and the resource is "won". The device gNB or UE gains access to resources until a Maximum Channel Occupancy Time (MCOT) is reached, provided that there is no transmission interruption exceeding a predetermined interval (e.g., 16 μ s).

If the CCA indicates that the resource is occupied, the device waits until transmission stops and then resumes the LBT procedure until the "backoff" time expires (typically monitored using a "backoff counter"). This ensures that there will be a minimum time for the resources to be idle for between transmissions. The duration of the contention window is typically randomly selected by each device within a defined range to mitigate collisions between multiple devices attempting to transmit simultaneously.

In systems that require CCA before transmission, each device applies an LBT period during the contention window and can only start transmission at the end of the contention window if the LBT procedure is successful.

Figure 1 shows an example where two devices/users (user 1 and user 2) are initially seeking access to the same resource, the Wi-Fi device is transmitting. The first device selects the shorter back-off time and starts transmitting first. The second device monitors the first device for transmissions during its LBT and therefore cannot start transmitting, and therefore the first device prevents the second device from transmitting.

In a system with uncoordinated, equal devices, this process ensures that the access landscape of all devices is equal. However, if multiple devices from a system or group attempt to utilize these resources, the allocation of access is not as fair. For example, multiple UEs may attempt to connect to a cellular base station using resources. If there are N devices, then multiple UEs will select N LBT durations, while for a pair of Wi-Fi devices, they will only obtain a single LBT duration to access the resources. Thus, a Wi-Fi device has only a 1/(N +1) chance of gaining access to a resource.

If N is large, the Wi-Fi device is unfairly blocked from accessing resources by the cellular system (which is actually a group of devices). In case of contention with N cellular devices, the probability of one Wi-Fi device gaining resource access may be calculated as:

wherein, C_winIs the maximum duration of the contention window (same Wi-Fi device and cellular device). In order to access resources, the Wi-Fi device must set a duration (t) that is longer than all N user choices_u) Short time (t)_wifi). The different values are plotted in fig. 2 according to the above equation, where the y-axis represents the probability of success for a Wi-Fi device and the x-axis represents the contention window size set by the Wi-Fi device.

The above examples are for reference only, and the exact fairness and utilization may vary.

Furthermore, if one of the cellular devices wins access, other cellular devices of the same system will be prevented from accessing the resources, even though they may share them due to their wireless protocol.

Therefore, there is a need for a system that allows for fair access to transmission resources between multiple device types and between groups.

Therefore, there is a need for an improved LBT procedure to achieve fair resource sharing.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

There is provided a method of resource sharing in a cellular communication system, the method being performed by a group of devices comprising: at each device, generating a seed for a pseudo random number generator algorithm, wherein the same seed is generated at each device; generating, using the seed and the pseudo-random number generator algorithm, a first value in a sequence of values generated by the pseudo-random number generator algorithm from the seed; generating a contention window size based on a first value generated by the pseudo-random number generator algorithm; and performing a listen-before-talk procedure and, if the listen-before-talk procedure indicates that a plurality of transmission resources are accessible, beginning transmission at the end of the contention window size.

Each device in the device group is a user device.

Each user equipment is connected to a common base station.

Each of the devices is a base station.

The seed is generated according to a time-varying parameter.

The seed is generated from a system time value.

The seed is further generated based on at least one of an identification value known to each device in the group of devices, a frequency reference for a plurality of resources that the device wishes to transmit, and a common data value known to all devices.

The seed is based at least in part on information received from the base station.

The pseudo-random number generator algorithm is configured by transmissions from the base station.

There is also provided a method of resource sharing in a cellular communication system, the method being performed by a group of devices comprising: generating, at each device, a contention window size using a contention window size reservation table, wherein the contention window size is selected from the contention window size reservation table using an index, and each device uses the same index and selects the same contention window size; and performing a listen-before-talk procedure and, if the listen-before-talk procedure indicates that a plurality of transmission resources are accessible, beginning transmission at the end of the contention window size.

Each device in the device group is a user device.

Each user equipment is connected to a common base station.

Each of the devices is a base station.

The index is generated according to a time-varying parameter.

The index is generated from a system time value.

The index is further based on at least one of an identification value known to each device in the group of devices, a frequency reference of a plurality of resources that the device wishes to transmit, and a common data value known to all devices.

The index is based at least in part on information received from the base station.

There is also provided a device group or a group of user devices configured to perform the above method.

Also provided is a non-transitory computer-readable storage medium, which may include at least one of the following group: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memories, programmable read-only memories, erasable programmable read-only memories, EPROMs, electrically erasable programmable read-only memories, and flash memories.

Drawings

Further details, aspects and embodiments of the invention will be described, by way of example, with reference to the accompanying drawings. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. To facilitate understanding, similar reference numerals have been included in the corresponding figures.

FIG. 1 illustrates an example of a contention window;

FIG. 2 is an access probability graph;

FIG. 3 is a schematic diagram of portions of a cellular network; and

fig. 4 is a flow chart of a method of determining a contention window.

Detailed Description

Those skilled in the art will recognize and appreciate that embodiments of the present invention are described below by way of example only, and that the teachings herein are applicable to a variety of alternatives.

The following disclosure provides an improved mechanism for fair sharing of resources between devices.

Fig. 3 shows a schematic diagram of three base stations (e.g., enbs or gnbs, depending on the particular cellular standard and terminology) that make up a cellular network. Typically, each base station will be deployed by one cellular network operator to provide geographic coverage to UEs in that area. The base stations form a wireless local Area Network (RAN). Each base station provides radio coverage for the UE in its area or cell. The base stations are interconnected by an X2 interface and connected to the core network by an S1 interface. As will be appreciated, the embodiments show only basic details in order to illustrate key characteristics of the cellular network.

Each base station includes hardware and software to implement the functions of the RAN, including communication with the core network and other base stations, transmission of control and data signals between the core network and the UEs, and maintaining wireless communication for the UEs associated with each base station. The core network includes hardware and software to implement network functions such as overall network management and control, and call and data routing.

As described below, a mechanism is provided to coordinate LBT or contention window durations to provide a more fair sharing of resources between devices. A group of UEs in a cellular network may be considered a single device group seeking access to transmission resources and may therefore coordinate their access requests to allow fair access between the group and the different devices. In order to comply with the regulations for using unlicensed resources, each UE must perform its own LBT procedure before attempting a transmission. However, the LBT procedure may be coordinated between UEs such that all UEs have the same listening time/contention window and thus start their transmissions at the same time. That is, each UE may select the same contention window size for transmission attempts.

Thus, the UEs in a group may be configured to select the same duration for the LBT period/contention window and then transmit at the end of that period. A group of UEs may be all UEs of a cell, beam, group of cells, group of beams, or a subset thereof, or other grouping configured at the system layer. Although all UEs start transmitting at the same time, the cellular system is configured and designed to efficiently share resources between UEs, and thus the system can operate as intended. Since all UEs are part of the same group, any interference between these UEs is a problem for the system itself and is not affected by the usage rules applicable to unauthorized resources shared between unrelated devices.

Since all dependent devices choose the same contention window size, rather than a non-dependent device contending with N other contention window sizes for access, the non-dependent device contends with only 1 contention window size. That is, if the non-relevant device selects a duration that is shorter than the duration used by the cellular device, the non-relevant device gains access and the cellular device does not. However, if the cellular device selects a shorter duration, all cellular devices gain access and non-associated devices do not. Thus, even though there may be any number of cellular devices, the non-associated device has an opportunity to gain access at 1/2 (if only two devices or groups compete). Thus, all competing devices or groups have equal access opportunities.

The randomness of the contention window is important for fair access to the transmission resources and therefore static values cannot be pre-configured. Furthermore, the transmission of values to or between UEs will require a large signalling overhead each time a contention window is required, which is unlikely to be feasible, thereby precluding centralized generation.

A pseudo-random algorithm is usually used which generates a distribution of values close to true random values, but always generates the same sequence of values for a given seed, thereby selecting random values for parameters such as LBT duration. Thus, using a common seed and an algorithm that synchronizes multiple devices allows for aligning the generated values.

The seed of the algorithm for generating the duration may be sent to each UE through higher layer signaling (e.g., RRC). This reduces overhead compared to sending multiple separate values, since only one value needs to be sent to each UE, which can then be used to generate multiple durations. Other types of signaling may be used, such as Downlink Control Information (DCI). DCI may enable more dynamic configuration because DCI messages are used for dynamic configuration and, statically and dynamically in time, may enable greater flexibility in group definition.

Each UE must use the same algorithm, which may be predefined by the standard or selected and signaled to each UE together with or independently of the seed value. The actual value of the seed value is not important if all UEs in the group use the same value.

Since the sequence of values generated by the algorithm is predictable, the values generated by a single device will only agree when each device has generated the same number of values; that is, the algorithm must be synchronized to be at the same point in its sequence. In the present case, if one device requires more contention window duration than another device, the algorithm will lose synchronization and generate different values even if they are seeded with the same value. For example, a first device may succeed in an access attempt and therefore not require a contention window, while a second device may not succeed and require a contention window. The two devices are then at different positions in the sequence and the algorithm cannot reliably generate the same contention window in future opportunities.

The above problem may be solved by synchronizing the algorithms at intervals, but this may be difficult to coordinate, especially for UEs that may be more difficult to coordinate. Once at least the devices lose synchronization, it is necessary to resynchronize all the devices. Periodic synchronization also requires additional network overhead.

Loss of synchronization can be addressed by using a new, common seed for each value to be generated. Assuming that each device uses the same seed, they will generate the same pseudo-random value (the first value in the sequence) in each case. This effectively resynchronizes each algorithm at each generated value because only the first value in the sequence is used and the algorithm has no chance of losing synchronization.

Examples of common reference values used as seeds or in generating seeds may include a time reference (reference), a frequency reference, an identity known to all related devices (e.g., cell ID, RNTI, group ID), or any data known to all devices, such as part of a common signaling message.

To ensure that the values used are random, the seed value must be varied over time so that it is different for each contention window generated (otherwise, if the same seed value is used, the first value generated in each sequence will be the same). Since the first value in the sequence is used, the same value will be generated if the same seed is used twice. It appears that the most direct reference to be used is the system time value, optionally in combination with other values such as an ID value or the like.

All devices in the network should have a common time value and therefore using the time reference as a seed should allow all devices to retain a common seed value. The resource identifier is utilized to provide a common reference for devices sharing the resource, e.g., in a MU-MIMO or frequency multiplexing device, a frequency or other related resource identifier may be used.

The use of the identification number (identification number) allows the group-specific seed to be used according to the grouped UEs up to the specific identification number used. Such identifiers may enable devices (e.g., UEs) associated with different cells to share the same resources if they do not belong to a common group. This may be particularly relevant for uplink transmissions where frequency resources need to be shared between UEs in different cells.

Thus, various combinations of values and parameters, or portions thereof, may be used as seed values. The actual value of the seed is irrelevant and therefore the most convenient source can be utilised.

In the case where devices in different cells are utilizing resource sharing and a common contention window, it is assumed that the slot timing of the cells is coordinated between the cells.

Fig. 4 shows a flow chart according to an embodiment of the above disclosure. At step 400, the device requires a contention window. At step 401, a seed for a correlation algorithm is generated. As described above, the seed may be based on one or more common reference values known to all relevant devices. For example, a time reference optionally combined with other values, such as an ID value. At step 402, a contention window is generated using the seed.

In the modified system, the generation algorithm and the seed may be replaced by an index to a predetermined table of contention window sizes, thereby simplifying the calculation of the random value. The reference may also be a sequence of values that the user may use in case multiple contention windows are needed before receiving the new value. The search process will instead calculate the window size using the algorithm described above. For example, the index of the table may be derived from the system time value so that all devices will select the same entry in the table. The system time value may be used directly, modified or combined with other parameters.

Or generally using a network configuration signal, the operations of the above process may be turned on or off for the device. For example, if the network detects the presence of other devices, the process may be activated to ensure fair sharing. Further, the configuration of seed generation may vary and be configured according to the device group. When a new device is active in the relevant area, the new device may be added or deleted from the group to allow all devices in the area that wish to share resources to align.

The above description is given in terms of uplink transmissions from a UE connected to a base station, however the same principles apply to other devices and configurations as well. For example, a set of base stations may utilize the procedure to share downlink resources, or a set of UEs may utilize the technique for communication between UEs (rather than to base stations).

Although any devices or apparatuses constituting the network part are not shown in detail, any devices or apparatuses constituting the network part may include at least a processor, a storage unit, and a communication interface, wherein the processor, the storage unit, and the communication interface are configured to perform the method of any aspect of the present invention. Further options and choices are described below.

The signal processing functions of embodiments of the present invention, and in particular the gNB and the UE, may be implemented using computing systems or architectures known to those skilled in the relevant art. Computing systems, such as desktop, laptop or notebook computers, handheld computing devices (PDAs, cell phones, palmtops, etc.), mainframes, servers, clients, or any other type of special or general purpose computing device may be used as may be suitable or appropriate for a particular application or environment. A computing system may include one or more processors, which may be implemented using a general-purpose or special-purpose processing engine such as a microprocessor, microcontroller or other control module.

The computing system may also include a main memory, such as a Random Access Memory (RAM) or other dynamic memory, for storing information and instructions to be executed by the processor. Such main memory may also be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor. The computing system may also include a Read Only Memory (ROM) or other static storage device for the processor that stores static information and instructions.

The computing system may also include an information storage system, which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a Compact Disc (CD), a Digital Video Drive (DVD), a read or write drive (R or RW), or other removable or fixed media drive. For example, the storage media may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by the media drive. The storage media may include a computer-readable storage medium having stored therein particular computer software or data.

In alternative embodiments, the information storage system may include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. For example, these components may include removable storage units and interfaces, such as program cartridges and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to the computing system.

The computing system may also include a communication interface. Such a communication interface may be used to allow software and data to be transferred between the computing system and external devices. In some embodiments, the communication interface may include a modem, a network interface (e.g., an ethernet or other NIC card), a communication port (e.g., a Universal Serial Bus (USB) port), a PCMCIA slot and card, and so forth. Software and data transferred via the communications interface are in the form of signals which may be electronic, electromagnetic, optical or other signals capable of being received by the communications interface medium.

In this document, the terms 'computer program product', 'computer-readable medium' and the like may be used generally to refer to tangible media such as memories, storage devices or storage units. These and other forms of computer-readable media may store one or more instructions for use by a processor, including a computer system, to cause the processor to perform specified operations. These instructions, generally referred to as 'computer program code' (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system to perform functions of embodiments of the present invention. Note that the code may directly cause the processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.

The non-transitory computer readable medium may include at least one of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, Read-Only memories, Programmable Read-Only memories, Erasable Programmable Read-Only memories, EPROMs, Electrically Erasable Programmable Read-Only memories (EEPROMs), and flash memories. In one embodiment, the functions of the elements are implemented using software, which may be stored in a computer-readable medium and loaded into a computing system using, for example, a removable storage drive. When executed by a processor in a computer system, the control module (in this example, software instructions or executable computer program code) causes the processor to perform the functions of the invention as described herein.

Furthermore, the inventive concept may be applied to any circuit for performing signal processing functions within a network element. It is further contemplated that, for example, a semiconductor manufacturer may use the concepts of the present invention in the design of a stand-alone device, such as a microcontroller and/or any other subsystem elements of a Digital Signal Processor (DSP) or application-specific integrated circuit (ASIC).

It will be appreciated that the above description, for clarity, describes embodiments of the invention with reference to a single processing logic. The inventive concept may, however, be equally implemented by a plurality of different functional units and processors to provide the signal processing functions. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors or configurable modular components such as FPGA devices.

Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the attached claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in any combination in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of methods, elements or method steps may be implemented by e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may only be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Furthermore, the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to "a", "an", "first", "second", etc., do not preclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the attached claims. In addition, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention, and that various modifications may be made by those skilled in the art. In the claims, the term "comprising" does not exclude the presence of other elements.

Claims (19)

1. A method of resource sharing in a cellular communication system, the method being performed by a group of devices, comprising:

at each device, generating a seed for a pseudo random number generator algorithm, wherein the same seed is generated at each device;

generating, using the seed and the pseudo-random number generator algorithm, a first value in a sequence of values generated by the pseudo-random number generator algorithm from the seed;

generating a contention window size based on a first value generated by the pseudo-random number generator algorithm; and

a listen-before-talk procedure is performed and if the listen-before-talk procedure indicates that multiple transmission resources are accessible, transmission begins at the end of the contention window size.

2. The method of claim 1, wherein each device in the device group is a user device.

3. The method of claim 2, wherein each user equipment is connected to a common base station.

4. The method of claim 1, wherein each device is a base station.

5. The method of any preceding claim, wherein the seed is generated from a time-varying parameter.

6. The method of any preceding claim, wherein the seed is generated from a system time value.

7. The method of claim 6, wherein the seed is further generated based on at least one of an identification value known to each device in the group of devices, a frequency reference for a plurality of resources that a device wishes to transmit, and a common data value known to all devices.

8. The method of claim 3, wherein the seed is based at least in part on information received from the base station.

9. The method of claim 3, wherein the pseudo-random number generator algorithm is configured by transmissions from the base station.

10. A method of resource sharing in a cellular communication system, the method being performed by a group of devices, comprising:

generating, at each device, a contention window size using a contention window size reservation table, wherein the contention window size is selected from the contention window size reservation table using an index, and each device uses the same index and selects the same contention window size; and

a listen-before-talk procedure is performed and if the listen-before-talk procedure indicates that multiple transmission resources are accessible, transmission begins at the end of the contention window size.

11. The method of claim 10, wherein each device in the device group is a user device.

12. The method of claim 11, wherein each user equipment is connected to a common base station.

13. The method of claim 10, wherein each device is a base station.

14. The method according to any of claims 10 to 13, wherein the index is generated according to a time-varying parameter.

15. The method of any of claims 10 to 14, wherein the index is generated from a system time value.

16. The method of claim 15, wherein the index is further based on at least one of an identification value known to each device in the group of devices, a frequency reference for a plurality of resources that a device wishes to transmit, and a common data value known to all devices.

17. The method of claim 11 or 12, wherein the index is based at least in part on information received from the base station.

18. A device group, characterized by being configured to perform the method of any of the preceding claims.

19. The device set of claim 18, wherein each device is a user device.

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