SYSTEMS AND METHODS FOR DYNAMIC BASE STATION UPLINK/DOWNLINK FUNCTIONAL SPLIT CONFIGURATION MANAGEMENT

Systems and methods for dynamic base station functional split configuration management are provided. In one embodiment, a system for base station functional split management for uplink fronthaul traffic comprises: a baseband controller coupled to a plurality of radio units via a fronthaul network, wherein the plurality of radio units comprise a signal zone from which uplink signals are combined by the base station: a split controller configured to dynamically select and control a functional split of a respective uplink receive chain between the baseband controller and each of the plurality of radio units: wherein the functional split defines a demarcation point on the receive chain prior to which processing operations are executed by a radio unit and after which processing operations are executed by the baseband controller: wherein the split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

BACKGROUND

Cloud-based virtualization of Fifth Generation (5G) base stations (also referred to as “gNodeBs” or “gNBs”) is widely promoted by standards organizations, wireless network operators, and wireless equipment vendors. Such an approach can help provide better high-availability and scalability solutions as well as addressing other issues in the network.

In general, a distributed 5G gNodeB can be partitioned into different entities, each of which can be implemented in different ways. For example, each entity can be implemented as a physical network function (PNF) or a virtual network function (VNF) and in different locations within an operator's network (for example, in the operator's “edge cloud” or “central cloud”). A distributed 5G gNodeB can be partitioned into one or more central units (CUs), one or more distributed units (DUs), and one or more radio units (RUs). The CU and DUs together are referred to as a baseband controller (BC). Each CU can be further partitioned into a central unit control-plane (CU-CP) and one or more central unit user-planes (CU-UPs) dealing with the gNodeB Packet Data Convergence Protocol (PDCP) and above layers of functions of the respective planes, and each DU configured to implement the upper part of physical layer through radio link control (RLC) layer of both control-plane and user-plane of gNodeB. In this example, each RU is configured to implement the radio frequency (RF) interface and lower physical layer control-plane and user-plane functions of the gNodeB. Each RU is typically implemented as a physical network function (PNF) and is deployed in a physical location where radio coverage is to be provided. Each DU is typically implemented as a virtual network function (VNF) and, as the name implies, is typically distributed and deployed in a distributed manner in the operator's edge cloud. Each CU-CP and CU-UP is typically implemented as a virtual network function (VNF) and, as the name implies, is typically centralized and deployed in the operator's central cloud.

In some implementations, each base station is configured to wirelessly communicate with each UE served by the base station using a respective subset of the RUs used with that base station. This respective subset of RUs for each UE is also referred to here as the “signal zone” (SZ) for that UE. In such implementations, downlink data is wirelessly transmitted to a given UE by wirelessly transmitting that downlink data from the RUs included in that UE's signal zone, and uplink data is wirelessly received from a given UE by combining data received at the RUs included in that UE's signal zone. The SZ used for transmitting data to a UE may be different from the SZ used for receiving data from the UE.

This type of base station can also be configured to support frequency reuse. “Frequency reuse” in the downlink refers to situations where separate downlink data intended for different UEs is simultaneously wirelessly transmitted to the UEs using the same physical resource blocks (PRBs) for the same cell but using different RUs. Frequency reuse in the uplink refers to situations where separate uplink data simultaneously wirelessly transmitted from different UEs using the same PRBs for the same cell is received using different RUs. In such situations, the reuse UEs are also referred to here as being “in reuse” with each other. For those PRBs where frequency reuse is used, each of the multiple reuse UEs is served by a different subset of the RUs, where no RU is used to serve more than one UE for those reused PRBs.

Cloudification and virtualization of network elements for a 5G gNodeB brings in a lot of benefits but also introduces challenges with respect to the fronthaul network through which the DUs and RUs communicate uplink and downlink user data and control traffic. For example, proposed use cases employing multiple-input multiple-output (MIMO) RU configurations and frequency reuse techniques complying with the standard open radio access network (O-RAN) function split can result in projected fronthaul traffic to exceed the 10 Gbps Ethernet bandwidth capacity of the fronthaul network.

SUMMARY

The embodiments of the present disclosure provide systems and methods for dynamic base station uplink split configuration management and will be understood by reading and studying the following specification.

In one example, a system for base station functional split management for uplink fronthaul traffic comprises: a baseband controller coupled to a plurality of radio units via a fronthaul network, wherein the plurality of radio units comprise a signal zone from which uplink signals are combined by a base station; a split controller configured to dynamically select and control a functional split of a respective uplink receive chain between the baseband controller and each of the plurality of radio units; wherein the functional split defines a demarcation point on the uplink receive chain prior to which processing operations are executed by a radio unit and after which processing operations are executed by the baseband controller; wherein the split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

In another example, a method for base station functional split management for uplink fronthaul traffic, wherein a base station comprises a baseband controller coupled to a plurality of radio units via a fronthaul network, wherein the plurality of radio units comprise a signal zone from which uplink signals are combined by the base station, the method comprising: determining one or more current operating parameters or conditions; dynamically selecting, based on the one or more current operating parameters or conditions, a functional split of a respective uplink receive chain between the baseband controller and each of the plurality of radio units, wherein the functional split defines a demarcation point on the uplink receive chain prior to which processing operations are executed by a radio unit and after which processing operations are executed by the baseband controller; wherein a split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

In another example, a system for base station functional split management for downlink fronthaul traffic comprises: a baseband controller coupled to a plurality of radio units via a fronthaul network; a split controller configured to dynamically select and control a functional split of a respective downlink transmit chain between the baseband controller and each of the plurality of radio units; wherein the functional split defines a demarcation point on the downlink transmit chain prior to which processing operations are executed by the baseband controller and after which processing operations are executed by a radio unit; wherein the split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

In another example, a method for base station functional split management for downlink fronthaul traffic, wherein a base station comprises a baseband controller coupled to a plurality of radio units via a fronthaul network, the method comprising: determining one or more current operating parameters or conditions; dynamically selecting, based on the one or more current operating parameters or conditions, a functional split of a respective downlink transmit chain between the baseband controller and each of the plurality of radio units, wherein the functional split defines a demarcation point on the downlink transmit chain prior to which processing operations are executed by the baseband controller and after which processing operations are executed by a radio unit; wherein a split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present disclosure. Reference characters denote like elements throughout figures and text.

DETAILED DESCRIPTION

FIGS.1and1Aare block diagrams illustrating examples of a virtualized wireless base station100on a VNF hosting platform on which the radio units described herein may be utilized. In the context of a fourth generation (4G) Long Term Evolution (LTE) system, a base station100may also be referred to as an “evolved NodeB” or “eNodeB”, and in the context of a fifth generation (5G) New Radio (NR) system, may also be referred to as a “gNodeB.” Base station100may be referred to as something else in the context of other wireless interfaces. Moreover, the radio units (RUs) discussed herein may alternately be described in different implementations as radio points (RPs) or remote antenna units (RAUs).

In the particular examples shown inFIGS.1and1A, the virtualized wireless base station100comprises a 5G gNodeB100partitioned into one or more central units (CUs)102, which include a central unit control-plane (CU-CP)116and one or more central unit user-planes (CU-UPs)118. In this example, the CU-CP116and CU-UPs118are both implemented as VNFs, but may be implemented in other ways in other implementations. The gNodeB100is further partitioned into one or more distributed units (DUs) and one or more radio units (RUs)106. In this example, the DUs105are composed of one or more DUs105, but may be implemented in other ways in other implementations.

In this example the virtualized 5G gNodeB100is configured so that each CU102is configured to serve one or more DUs105and each DU105is configured to serve one or more RUs106. In the particular configuration shown inFIGS.1and1A, a single CU102serves a single DU105, and the DU105serves three RUs106. However, the particular configurations shown inFIGS.1and1Aare only examples. In other embodiments, other numbers of CUs102, DUs105, and RUs106can be used. Also, the number of DUs105served by each CU102can vary from CU102to CU102. Likewise, the number of RUs106served by each DU can vary from DU105to DU105.

Moreover, although the following embodiments are primarily described as being implemented for use to provide 5G NR service, it is to be understood that the techniques described here can be used with other wireless interfaces (for example, fourth generation (4G) Long-Term Evolution (LTE) service) and references to “gNodeB” used in this disclosure can be replaced with the more general term “base station” or “base station entity” and/or a term particular to the alternative wireless interfaces (for example, “enhanced NodeB” or “eNB”). Furthermore, it is also to be understood that 5G NR embodiments can be used in both standalone and non-standalone modes (or other modes developed in the future), and the following description is not intended to be limited to any particular mode. Also, unless explicitly indicated to the contrary, references to “layers” or a “layer” (for example, Layer 1, Layer 2, Layer 3, the Physical Layer, the MAC Layer, etc.) set forth herein refer to layers of the wireless interface (for example, 5G NR or 4G LTE) used for wireless communication between a base station and user equipment). The CU102implements Layer 3 and non-real-time critical Layer 2 functions for the base station100. Each DU105is configured to implement the time-critical Layer 2 functions and at least some of the Layer 1 (also referred to as the Physical Layer) functions for the base station100. In this example, each RU106is configured to implement a radio frequency (RF) interface184and Layer 1 functions for the base station100that are not implemented in the DU105.

In general, the virtualized gNodeB100is configured to provide wireless service to various numbers of user equipment (UEs)108using one or more cells110(only one of which is shown inFIGS.1and1Afor ease of illustration). Each RU106includes or is coupled to a respective set of one or more antennas112via which downlink RF signals are radiated to UEs108and via which uplink RF signals transmitted by UEs108are received.

In one configuration (used, for example, in indoor deployments), each RU106is co-located with its respective set of antennas112and is remotely located from the DU105and CU102serving it as well as the other RUs106. In another configuration (used, for example, in outdoor deployments), the respective sets of antennas112for multiple RUs106are deployed together in a sectorized configuration (for example, mounted at the top of a tower or mast), with each set of antennas112serving a different sector. In such a sectorized configuration, the RUs106need not be co-located with the respective sets of antennas112and, for example, can be co-located together (for example, at the base of the tower or mast structure) and, possibly, co-located with its serving DUs105. Other configurations can be used.

The virtualized gNodeB100is implemented using a scalable cloud environment to define a baseband controller (BC)120in which resources used to instantiate each type of entity can be scaled horizontally (that is, by increasing or decreasing the number of physical computers or other physical devices) and vertically (that is, by increasing or decreasing the “power” (for example, by increasing the amount of processing and/or memory resources) of a given physical computer or other physical device). The BC120can be implemented in various ways.

For example, the BC120can be implemented using hardware virtualization, operating system virtualization, and application virtualization (also referred to as containerization) as well as various combinations of two or more of the preceding. The BC120can be implemented in other ways. For example, as shown inFIGS.1and1A, the BC120is implemented in a distributed manner. That is, the BC120is implemented as a distributed scalable cloud environment120comprising at least one central cloud114and at least one edge cloud115.

In the examples shown inFIGS.1and1A, each RU106is implemented as a physical network function (PNF) comprising radio transceiver circuitry and is deployed in or near a physical location where radio coverage is to be provided. In this example, each DU is implemented with one or more DU virtual network functions (VNFs) and may be distributed and deployed in a distributed manner in the edge cloud115. Each CU-CP116and CU-UP118is implemented as a virtual network function (VNF). The CU-CP116and CU-UP118may be centralized and deployed in the central cloud114as shown inFIG.1.FIG.1Aillustrates an alternative implementation toFIG.1where the CU-CP116and CU-UP118are instead deployed in the edge cloud115. In the examples shown in theseFIGS.1and1A, the CU102(including the CU-CP116and CU-UP118) and the entities used to implement it are communicatively coupled to each DU105served by the CU102(and the VNFs used to implement each such DU105). In some embodiments, the CU102and DU105are communicatively coupled over a midhaul network128(for example, a network that supports the Internet Protocol (IP)). In the examples shown inFIGS.1and1A, each the DUs105used to implement a DU are communicatively coupled to each RU106served by the DU105using a fronthaul network125(for example, a switched Ethernet network that supports the IP).

The scalable cloud environment utilized for BC120comprises one or more cloud worker nodes122that are configured to execute cloud native software124that, in turn, is configured to instantiate, delete, communicate with, and manage one or more virtualized entities126of a base station (for example, a CU-CP116, CU-UP118, and DU105for a gNodeB100). The cloud worker nodes122may comprise respective clusters of physical worker nodes (or virtualized worker nodes if implemented in combination with hardware virtualization), the cloud native software124may comprise a shared host operating system, and the virtualized entities126comprise containers. In another example, the cloud worker nodes122comprise respective clusters of physical worker nodes, the cloud native software124comprises a hypervisor (or similar software), and the virtualized entities126comprise virtual machines.

In the example shown inFIGS.1and1A, the scalable cloud environment for BC120includes a cloud “master” node132. There are certain responsibilities that the cloud “master” node132has as far as instantiation of cloud worker nodes122and clustering them together. The cloud master node132is configured to implement management and control plane processes for the worker nodes122in a cluster. In some examples, the cloud master node132is configured to determine what runs on each of the cloud worker nodes122, which can include scheduling, resource allocation, state maintenance, and monitoring. In some examples, the cloud master node is configured to manage the lifecycle, scaling, and upgrades of workloads (such as containerized applications) on the cloud worker nodes122.

Each of the virtual network functions, DU105, CU-CP116, and CU-UP118is implemented as a software virtualized entity126that is executed in the scalable cloud environment120on a cloud worker node122under the control of the cloud native software124executing on that cloud worker node122. In the following description, a cloud worker node122that implements at least a part of a CU102(for example, a CU-CP116and/or a CU-UP118) is also referred to here as a “CU cloud worker node”122, and a cloud worker node122that implements at least a part of a DU105is also referred to here as a “DU cloud worker node”122.

In the example embodiment of a gNodeB100base station, the CU-CP116and the CU-UP118are each implemented as a respective virtualized entity126executing on the same cloud worker node122. The DU105may be implemented as a virtualized entity126executing on the same cloud worker node122or a different cloud worker node122. In other configurations and examples, the CU102can be implemented using multiple CU-UPs118using multiple virtualized entities126executing on one or more cloud worker nodes122. In another example, multiple DUs105(using multiple virtualized entities126executing on one or more cloud worker nodes122) can be used to serve a cell, where each of the multiple DUs105serves a different set of RUs106. Moreover, it is to be understood that the CU102and DU105can be implemented in the same cloud (for example, together in an edge cloud115). Other configurations and examples can be implemented in other ways. The various VNFs are configured to be activated to make them service ready using for example, service configurations with an Operations and Maintenance (OAM) entity or Device Management System (DMS).

The base station100is configured to support frequency reuse. As noted above, “frequency reuse” in the downlink refers to situations where separate downlink user data intended for different UEs108is simultaneously wirelessly transmitted to the UEs108using the same physical resource blocks (PRBs) for the same cell110but using different RUs106. Frequency reuse in the uplink refers to situations where separate uplink data simultaneously wirelessly transmitted from different UEs108using the same PRBs for the same cell110is received using different RUs106. Such reuse UEs108are also referred to here as being “in reuse” with each other. For those PRBs where frequency reuse is used, each of the multiple reuse UEs108is served by a different subset of the RUs106, where no RU106is used to serve more than one UE108for those reused PRBs

FIG.2illustrates the example of an RU106that is deployed and coupled to the DU105via fronthaul network125. DU105is implemented by one or more virtualized entities126configured to execute code to realize aspects of the DU105in operation as discussed herein. RU106comprises a processor206(for example, a central processing unit (CPU)) and a memory207which together store and execute code to realize aspects of the RU106in operation as discussed herein. The RU106also includes radio transceiver211circuitry (which may comprise, for example, amplifiers, RF filters, frequency converters, and the like) to implement uplink and downlink communication paths.

For the transmit and receive chains illustrated byFIGS.3and4, the amount of fronthaul traffic generated from uplink and downlink communications between the DU105and an RU106can vary as a function of which DU/RU functional split is being used. In particular,FIG.3illustrates various physical-layer operations specified for 5G NR for a transmit chain300for a Physical Downlink Shared Channel (PDSCH), andFIG.4illustrates various physical-layer operations specified for 5G NR for a receive chain400for a Physical Uplink Shared Channel (PUSCH).

The physical-layer processing operations shown inFIGS.3and4are individually described in the 3GPP specifications (either explicitly or, in the case of some receive chain operations, implicitly by inverting the individual description of the corresponding transmit chain operations). It is to be understood thatFIGS.3and4each illustrate only one example and that the present disclosure can be used with other wireless interfaces (for example, 4G LTE). Moreover, embodiments disclosed herein may be used to dynamically control DU/RU functional split configurations with other physical channels (for example, the Physical Broadcast Channel (PBCH), Physical Downlink Control Channel (PDCCH), Physical Random Access Channel (PRACH), and Physical Uplink Control Channel (PUCCH)).

DU/RU functional split configurations may further be applied to still other physical channels such as but not limited to, Demodulation Reference Signal (DMRS), Primary Secondary Signal (PSS), Secondary Synchronization Signal (SSS) and/or Channel State Information Reference Signal (CSI-RS).

It should be understood that additional operations not shown inFIGS.3and4may also be included, for example, to support fronthaul transmission (for example, IQ compression decompression). Also, the particular sequence of operations may differ from what is shown inFIGS.3and4. For example, the sequence of operations is dependent on the functional DU/RU functional split used between the DU105and RU106(or similar entities) and the type of RU106employed as discussed below.

Base stations typically implement the physical-layer processing operations individually in accordance with the 3GPP specifications, with each of the various physical-layer processing operations described in the 3GPP specifications being implemented as a discrete, separate operation. The input for each such discrete operation is either the output of a different physical-layer operation or the output of the MAC layer (for the downlink) or the RF block (for the uplink). The data used as the input for each discrete operation is typically read from memory, and the data that is output by each discrete operation is typically written to memory. Also, each such discrete operation typically performs its processing on a transport-block-by-transport-block basis, buffering data as necessary. However, as noted above, with the conventional approach, at least some hardware acceleration is typically necessary in order to meet the stringent timing requirements specified for the wireless interface, which makes the conventional approach less suitable for deployment in cloud-based environments.

With the embodiment described herein, the DU/RU functional split refers to a demarcation point that defines which physical-layer operations are performed by the DU105, and which physical-layer operations are performed by the RU106. It should be noted that the demarcation point for the transmit chain300may be different than for the receive chain400. Problems or disadvantages that can develop from a non-optimized DU/RU functional split in the transmit chain300include: 1) High traffic levels or congestion on the fronthaul network125(where in some use cases the traffic may exceed the 10 Gbps bandwidth capacity of the fronthaul network); 2) Limited scalability (for example, features like carrier aggregation and frequency reuse are processing resource intensive and may strain the processing capabilities of the DU105); 3) RU processing underutilization (for example, an RU may be equipped with relatively powerful processing resources that are not fully utilized); 4) Inefficient locality utilization (for example, it should be straightforward for an RU106to manage downlink retransmissions to a UE108as needed (because the UE108is in closer proximity to the RU106than the DU105), but under the standard open radio access network (O-RAN) split utilizing the RU106for this purpose cannot be realized); 5) The standard O-RAN split does not provide the RU106with the ability to address individual UEs.

Referring now toFIG.3, the physical layer processing operations are illustrated for the transmit chain300for the PDSCH in accordance with some embodiments of the present disclosure. The physical layer processing operations for the transmit chain300for the PDSCH include a transport block (TB) Cyclic Redundancy Code (CRC) attachment operation302, a code block (CB) segmentation and CRC attachment operation304, a low density parity check (LDPC) channel coding and rate matching operation306, a code block (CB) concatenation and scrambling operation308, a modulation operation310that may include a compression operation312(optional depending on selected split), layer mapping (LM) and precoding operation314that may include a decompression operation (optional, depending on whether compression operation312is utilized), a resource element mapping operation316, and a time domain processing operation318(which may include an inverse fast Fourier transform (IFFT) and cyclic prefix (CP) addition operations).

In one exemplary implementation for the 5G NR PDSCH operations shown inFIG.3, the computationally intensive channel coding operations, including, for example, the transport block CRC attachment operation302, the code block segmentation and CRC attachment operation304, and LDPC channel coding306may be combined and replaced with a single transfer function that is configured to map each of the universe (or set) of relevant, valid inputs to the transport block CRC attachment operation302to a corresponding output of LDPC channel coding306.

FIG.4illustrates example physical layer processing operation blocks for a receive chain400for the PUSCH in accordance with some embodiments of the present disclosure. The physical layer processing operations for the receive chain400for the PUSCH include a time domain processing operation428(which may include fast Fourier transform (FFT) and/or cyclic prefix (CP) removal operations), a physical resource block (PRB) de-mapping operation454, a channel estimation and interpolation operation456, a Minimum Mean Square Error (MMSE)/Interference Rejection Combining (IRC) equalization and combiner operation460, a layer de-mapping operation462, a soft demodulation operation464, a de-scrambling operation466, and a user and control data demultiplexing operation468. For the user data, the receive chain400further includes a code block (CB) segmentation operation470, a rate de-matching and LDPC channel decoding operation474, a code block CRC decoding operation476, a code block concatenation operation478, and a transport block CRC decoding operation480.

In another exemplary implementation for the 5G NR PUSCH operations shown inFIG.4, the computationally intensive channel de-coding operations, including, for example, the rate de-matching operation, the LDPC decoding operation, the code block CRC decoding operation476, the code block concatenation operation478, and the transport block CRC decoding operation480may be combined and replaced with a single transfer function that is configured to map each of the universe (or set) of relevant, valid inputs to the rate de-matching operation to a corresponding output of the transport block CRC decoding operation480.

With embodiments of the present disclosure, the base station100comprises a split controller210(for example, an L1 split controller) that manages the DU/RU functional split demarcation point for the transmit chain300and receive chain400. In some embodiments, the functions of the split controller210may be distributed between the DU105and the RU106, as shown inFIG.2. For example, in some embodiments, functions of the split controller210are implemented as a part of the Layer 2 functions176implemented by the DU105. This can be implemented as a part of a MAC scheduler178implemented in the DU105. In some embodiments, the split controller210may be at least partially implemented in the RU106as one or more applications executed by the processor206.

The DU/RU functional split demarcation point may be determined at setup (for example, manually selected by a technician) or dynamically determined and reconfigured by the split controller210during runtime in response to changing parameters or conditions. For example, the DU/RU functional split demarcation point may be determined for a given protocol data unit (PDU) (such as, DLSCH, downlink control information (DCI), management information block (MIB), for example) based on consideration such as DU load, system load, subcarrier spacing, arrival time, fronthaul bandwidth and/or congestion, RU processing capacity, inter-switch link capacity, scaling considerations, and/or equipment interoperability. Additionally, the DU/RU functional split can also be chosen based on the application type, one example would be if there is a desire to serve ultra-reliable low latency communications (URLLC) UEs.

FIG.5illustrates at 500 example DU/RU functional splits that may be dynamically implemented by the split controller210at different points in a PDSCH processing chain (such as processing chain300shown inFIG.3). In this example, a PDSCH processing chain is illustrated for a single transport block (TB) assuming 4×4 mode, 270 PRBs, and a maximum code rate, with four spatial multiplexing (SM) layer mapped to four RU106antennas112. However, the transmit processing chain may instead comprise other configurations of TBs, SM layers, code rates, and RU antennas. For example, in some embodiments the PDSCH processing chain may instead comprise two TBs with eight spatial multiplexing (SM) layers that are mapped to mapped antennas112at the RU106. It should be understood that the functional splits illustrated inFIG.5are intended as non-limiting examples and other splits between other operational processes may be implemented.

For the example ofFIG.5, the least amount of fronthaul125data traffic is generated when the split controller210selects DU/RU functional split Option-1 (shown at510), which is referred to herein as the “early split”510. With the early split510, the DU105simply forwards the PDSCH payloads to the RU106. In other words, all of the processing blocks of the processing chain300are performed by algorithms executed by the processor206of the RU106. The early split510fully offloads downlink processing from the DU105to RU106so that the DU105can spend its processing capacity for uplink or other tasks. It also generates the lowest fronthaul125traffic and is close to the total sector throughput. This option can yield reduced jitter buffer between the DU105and RU106, and L1 scaling is only limited by number of RUs106coupled to the DU105since each RU106act as an independent processing element. The early split510, however, relies heavily on ample processing capacity at the RU106and may be less appropriate when the processing capacity at the RU106is limited.

The DU/RU functional split Option-2, which is referred to herein as the “delayed split”512generates only a little more traffic on the fronthaul network125than the early split510. Here, the DU105performs the processing blocks and encodes DL channels up to scrambling308. In other words, the DU105performs the processing blocks prior to modulation310. The scrambled payload is sent to RU106to execute the modulation310operation and the remaining processing blocks of the processing chain300. The delayed split512can be selected by the split controller210for instances where the processing capacity of the DU105is scalable so that processing tasks for the processing chain300can be evenly divided between the DU105and the RU106. The delayed split512also supports small subcarrier spacing (for example, spacing of 15 kHz or 30 kHz) with increased duration time slots where the DU105has the adequate capacity to process such downlink data. The delayed split512also results in a lower fronthaul125traffic rate compared to a standard O-RAN split so that L1 scaling is also possible with this option. That said, the delayed split512may be limited in practicality in applications where a delayed availability of MAC PDUs at the DU105can overload the processing at the DU105, thus interfering with the processing of an upcoming slot.

The DU/RU functional split Option-3, which is referred to herein as the “modulation split”514, has processing through the modulation310and the optional compression312processing blocks performed at the DU105. The resulting modulated and compressed data is transported via the fronthaul125to the RU106to execute the balance of the processing blocks of the processing chain300. In some embodiments, the compression performed at312may comprise standard O-RAN compression techniques. In other embodiments, the compression312may comprise an expanded bit depth compression as discussed below. The modulation split514can result in the generation of less fronthaul traffic than the O-RAN split when compression312is performed at the DU105, and therefore may be utilized to reduce fronthaul125traffic in cases where the RU106has excess in computing capacity, but not a sufficient excess to implement a delayed split512. Like the delayed split512, the modulation split514may be limited in practicality in applications where a delayed availability of MAC PDUs at the DU105can overload the processing at the DU105, thus interfering with the processing of an upcoming slot.

The DU/RU functional split Option-4 comprises what is referred to as the standard O-RAN 7.2 split (and can be either Category-A or Category-B), which is referred to herein as the “O-RAN split”516. With the O-RAN split516, time domain processing318is performed at the RU106, but the prior processing operations are performed at the DU105. Although the O-RAN split516produces the highest fronthaul125traffic rate, and may limit the use and scalability of features such as frequency reuse as discussed above, the split controller210may still select the O-RAN split516for several reasons. For example, the split controller210may select the O-RAN split516where the RU106does not have the processing capacity to execute the algorithms for performing the modulation split514. The split controller210may select the O-RAN split516where it detects that the RU106is an O-RAN 7.2 compliant device and does not comprise split controller210or other functionality capable of implementing the other split options.

It should be appreciated that the split controller210can also manage the DU/RU functional split between other payloads communicated between the DU105and RU106in addition to the PDSCH. For example, DU/RU functional splits for the Physical Broadcast Channel (PBCH), Physical Downlink Control Channel (PDCCH), Physical Random Access Channel (PRACH), Physical Uplink Shared Channel (PUSCH), and Physical Uplink Control Channel (PUCCH) payloads can each respectively be dynamically controlled and adjusted by the split controller210in the same or similar manner as described with respect toFIG.5. In each case, the split controller210can dynamically, or at the time of system startup, determine where the demarcation point is located, based on manually entered settings, or detected current system and/or fronthaul network parameters and operating conditions. For example,FIG.5Aillustrates demarcation points for early split510, delayed split512, modulation split514, and O-RAN split516configurations for PBCH and PDCCH payloads. The fundamental demarcation points of the DU/RU functional split are equivalent in each case. That is, the early split510places the most processing burden on the RU106(forwarding the baseline channel data on the fronthaul125) while the O-RAN split516places the least processing burden on the RU106(only the time domain processing performed at the RU). For the modulation split514(or demodulation split in the case of uplink traffic), the fronthaul125carries modulated (and optionally compressed) payloads.

In some embodiments, the DU/RU functional split for uplink fronthaul traffic may involve the split controller210taking additional or alternate factors into consideration. As an example, for uplink fronthaul traffic, a consideration may be to establish a DU/RU functional split that meets an optimum signal-to-noise ratio (SNR) for a target block error rate (BLER) performance while at same time reducing fronthaul125throughput between the RU106and DU105. For LTE base stations, it should be understood that references to the DU105in this description would instead refer to the eNB. In some embodiments, an optimum DU/RU functional split on an uplink data channel will be picked by split controller210for each UE108individually in a slot (for 5G) or subframe (for 4G) based on initial measurements from a physical random access channel (PRACH), sounding reference signal (SRS) channel, and/or a physical uplink control channel (PUCCH), which can be considered in conjunction with knowledge of the split controller210regarding how many RU106form a particular signal zone (combining zone) in which uplink signals are being combined.

It should be appreciated that an absence of macro RF interference and reuse RF interference neglects gains that would be realized from having interference rejection combining (IRC) implemented in the DU105. That said, the same IRC performance can be obtained through minimum mean square error (MMSE) combining of the antennas112at all RUs106, and then later combining equalized symbols at the DU106. In that case, the RUs106could send an average noise variance per PRB as side info (as discussed below).

Even in the presence of macro or reuse RF interference, a sub-optimal but still advantageous solution is to perform IRC at the RU's antennas112and MMSE RU combining at the DU105. The advantage of the split controller210applying such a DU/RU functional split would be the reduction in fronthaul125throughput as well as reduced processing load at the DU105. In other embodiments, IRC across the plurality or RU106in a combining zone can also be optionally executed at one of the base station's RUs106by opening up one or more communications channels between the RUs106so that they can communicate with each other. In some embodiments, for UEs108that are not participating in multi-RU combining in the uplink, the split controller210can adjust the DU/RU functional split so that uplink decoding operations can be completely offloaded to the RU106so that traffic with decoded bits is transported over the fronthaul125to the DU105.

FIG.6provides an alternate illustration at600of an uplink receive chain for a Physical Uplink Shared Channel (PUSCH) such as previously illustrated inFIG.4. InFIG.6, the primary processing blocks of interest include a time domain processing operation620(which may include fast Fourier transform (FFT) and/or cyclic prefix (CP) removal operations), channel estimation and interpolation operation622, equalization and antenna combining operation624, an inverse discrete Fourier transform (IDFT) operation626(which would be optional as being applicable for single-carrier frequency-divisional multiple access (SC-FDMA) waveforms), a demodulation log-likelihood ratio (LLR) operation628, and a channel decoding operation630.

InFIG.6, split option A demarks the standard O-RAN split, and this is referred to herein as the O-RAN split640. As discussed above, with this uplink O-RAN split640, time domain processing620is performed at the RU106, but the remaining processing operations of the uplink receive chain are performed at the DU105. In some embodiments, the IQ symbols output of the FFT operation are compressed to m bits before transmission over the fronthaul125. For an O-RAN compliant implementation, the m bit compression would comprise 9-bit compression, but other implementations may utilize other m values. The compression ratio achieved by the compressions discussed herein is defined as the ratio of compressed symbols transmitted over the fronthaul125to the IQ symbol rate as observed received at the RU antenna112. As such, the achieved compression ratio is independent of the number of antennas, SM layers, modulation, coding and transport block (TB) size. A lower compression ratio translates to a lower data rate on the fronthaul network125. High performance gain is obtained from the O-RAN split640because the uplink signals from multiple RU106are combined at the DU105. With this functional split option, multiple antennas originated from different RUs106can also be combined at the DU105using IRC. In absence of RU combining, other functional split options can be expected to achieve better fronthaul rate with the same performance.

InFIG.6, split option B is equivalent to option A, except that channel estimation622and associated modules are moved from being executed on the DU105to the RU106, to reduce processing load on the DU105. This is therefore referred to herein as the estimation split642. The fronthaul125data rate for an estimation split642will be higher than the O-RAN split640, not only because traffic comprising compressed channel estimates are now on the transported on the fronthaul125, but additional traffic is generated to transmit estimated noise for the MMSE equalizer to measure. An estimation split642therefore may be selected by the split controller210to help to reduce processing load on the DU105, but at the cost of increased throughput on the fronthaul125. The channel estimation and IQ symbols output of the FFT operation may also be compressed in this split option to m bits before transmission over the fronthaul125.

Split option C comprises performing the uplink processing operations at the RU106up to equalizing and combining antennas operation624. This is therefore referred to herein as the equalization-combining split644. Equalized symbols along with side information is sent over fronthaul125for processing or multi-RU combining at the DU105. At the equalizing and combining antennas operation624performed at the RU106, the received signals at each RU antenna112are equalized and combined before transmission on the fronthaul125. Each RU106performs IRC for its own antennas112(which may include sets of 2, 4, 8, etc. antennas). With the equalization-combining split644, equalized samples along averaged noise variance per antenna112are transmitted as side information over fronthaul125to achieve MMSE equalization and achieve RU combining at the DU105. The compression ratio efficiency of this option is independent of the number of RU antennas112and the modulation scheme, but does vary depending on the SM layers. Better compression is obtained from the equalization-combining split644than the O-RAN split640with an option of multi RU combining at the DU105using MMSE equalization. The IQ symbols output of the equalizing and combining antennas operation624may also be compressed in this split option to n bits before transmission over the fronthaul125.

The expression below provides an example function illustrating how equalized symbols c can be estimated and combined from each RU106at the DU105.

where Ĥ is channel frequency response, σn2is noise variance, Y is IQ for data symbols, and {circumflex over (X)} is equalized & combined symbols. In this equation, the numerator is quantized to 8 bit I & Q per sub-carrier and transmitted over the fronthaul125along with 4 bytes of side information, averaged per the PRB scale factor by the denominator.

Split option D comprises performing the uplink processing operations at the RU106up to the IDFT operation626, thus operationally performing IDFT calculations on the RU106to further reduce processing load on the DU105. This is therefore referred to herein as the IDFT split646. This additional processing would be applicable for implementations that have DFT-precoded uplink traffic (such as for SC-FDMA), and the resulting the fronthaul125data rate is equivalent as for the equalization-combining split644. The IQ symbols output of the IDFT operation626may also be compressed in this split option to n bits before transmission over the fronthaul125.

Split option E comprises performing the uplink processing operations at the RU106up though the demodulation LLR operation628and thus referred to herein as the demodulation split648. Demodulation is performed at the RU106and the demodulated soft decisions per layer are transmitted over the fronthaul125to the DU105. At the DU105, soft decisions from multiple RUs106are received and combined prior to the channel decoding630to improve SNR performance. The compression ratio archived by the demodulation split648is independent of the RU antennas112, but will depending on both the modulation used and the number of SM layers, where lower modulation results in higher compression. The soft decisions output of the demodulation LLR operation628may also be compressed in this split option to p bits per layer before transmission over the fronthaul125.

Split option F comprises performing the uplink processing operations at the RU106up through the decoding operation630. With this split, the complete uplink layer-1 processing is performed in the RU106. This is therefore referred to as the late split650. Decoding of the demodulated soft decision is done at RU106, and the resulting decoded bits and decoded transport block is transmitted on the fronthaul125to the DU105. As the DU105receives decoded transport blocks from the multiple RUs106, no RU combining can be performed by the DU105with this split option. The late split650, however, does achieve the lowest compression ratio and thus the lowest fronthaul rate of the various uplink DU/RU functional split options.

As discussed above, a baseband controller120(for example, a DU) may be coupled to a plurality of RU106serving any particular cell110and the split demarcation points for each RU106may be independently adjusted by the split controller210. For example,FIG.7illustrates a DU105coupled via fronthaul network125to a first RU710, a second RU712and a third RU714. In this example, UE720, UE722, UE724, and UE726are within a cell110served by RU710, RU712, and RU714. UE720, UE722, and UE724are physically isolated from each other, and therefore can reuse PRBs, which effectively triples the potential traffic carried by the fronthaul network125. UEs720,722, and724all utilize a first bandwidth partition (BWP) having a 15 kHz sub-carrier spacing (SCS) shown as BWP-0. UE726instead utilizes a second BWP having a 30 kHz SCS shown as BWP-1. In this example, the RU712is a relatively low power RU. The split controller210may therefore select an O-RAN split for RU712, or another DU/RU functional split option that does not cause the RU720to exceed its processing capacity. The RU710and RU714both comprise processing capacities that can fully implement any of the possible DU/RU functional split options. Accordingly, the split controller210can select split options based on SCS or other considerations. Moreover, the split controller210can not only select a functional split option for RU710that is different than for RU712or RU714, the split controller210can also select split options on a per BWP bases for any one RU. For example, UE724communicates via BWP-0 while and UE726communicates via the BWP-1. The split controller210can select a first DU/RU functional split option on RU714tailored for the traffic carried over BMW-0, while also selecting a different second DU/RU functional split option on RU714tailored for the traffic carried via BWP-1.

FIGS.7A and7Bare diagrams that illustrate example dynamic uplink split scenarios for different combinations of RUs and UEs. InFIG.7A, a first RU (shown at734-1) and a second RU (shown at734-2) are both within the combining zone732for a UE736. The contributing RUs are determined by PRACH, SRS, and PUCCH channel processing. In this scenario, there is a macro and/or reuse interference source730affecting UE736's signals with both RU734-1and RU734-2. Here, the split controller210may select the split option A (O-RAN split640) as the optimum configuration since the interference rejection combining of all RU antennas when performed at the DU105provides performance gain due to better interference cancellation.

InFIG.7B, the UE experience either partial or zero macro and reuse interference zones.

Referring to UE738, it can be seen that RU734-4and RU734-5are both in the combining zone750for this UE. In the absence of interference, the covariance matrix in the IRC receiver at the DU105reduces to a diagonal matrix and is therefore effectively equivalent to a MMSE equalizer. The split controller210selects a split where this MMSE equalization and combining can be performed at the RUs734-4and734-5and where combining of uplink signals from the RUs is performed at the DU105to achieve fronthaul network125traffic reduction. To combine multiple RUs at the DU105, each RU will send equalized & combined symbols along with averaged noise variance per PRB as side info. Combining the IQ across multiple antennas within each RU saves fronthaul network125bandwidth. Here, the split controller210may select the split option C (Equalization-Combining split644) as the optimum configuration, obtaining substantially equivalent performance as split option A (O-RAN split640) with respect to fronthaul network125traffic reduction. Another, but sub-optimal, solution is for the split controller210to select split option E (Demodulation Split648) which performs soft decision combining of the uplink signals from the RUs in the DU105. This split option E can achieve some fronthaul network125traffic savings for lower modulation schemes (for example, QPSK & 16 QAM) than split option C. Note that for 64 QAM modulating, split option C is optimal for both performance and fronthaul network125traffic savings.

Referring now to UE740inFIG.7B, there is only RU743-3in its combining zone752, and it is in proximity to macro/reuse interference source730. In the absence of another RU in combining zone752, no performance gain would be achieved by sending IQ over the fronthaul network125and performing decoding at the DU105. Accordingly, in this scenario the split controller210may select split option F (Late Split650) for this UE740so that fronthaul network125savings can be achieved by performing IRC within the RU734-3.

Referring now to UE742inFIG.7B, the RU734-3and RU734-5are in combining zone754for this UE. RU734-3is seeing interference from source730and will perform IRC combining across its antennas whereas RU734-5is not seeing interference and can perform MMSE combining. In this scenario, the split controller210may select either split option C or split option E, which can be used to perform RU combining in DU105based on fronthaul network125bandwidth availability.

Referring now to UE744inFIG.7B, RU734-4is the only RU in the combining zone756for this UE. In absence of any interference or another RU in combining zone756, the split controller210may select split option5so that decoding is accomplished within the RU735-4.

FIG.8is a flow chart illustrating a method800for dynamic functional split configuration between a baseband controller and radio units for a base station, such as base station100disclosed above. It should be understood that method800may be implemented using any one of the embodiments described above. As such, elements of method800may be used in conjunction with, in combination with, or substituted for elements of any of the embodiments described herein. Further, the functions, structures, features, and other description of elements for such embodiments described herein may apply to like named elements of method800and vice versa.

As noted above, a base station can be configured to implement the processing associated with method800. More specifically, the processing associated with method800can be implemented primarily as a part of the Layer 2 functions176implemented by the base station100(by a split controller that is stand-alone or part of the MAC scheduler178) and/or applications executed by the processor206of the RU106, with support from the other functions implemented by the base station100.

The method begins at810with determining, with a split controller, when a radio unit supports dynamic functional split configuration. For example, in some embodiments, a RU may not comprise the functionality to implement anything other than the standard O-RAN split. As such, when the RU cannot support dynamic split configuration, the method proceeds to812with processing transport blocks using an O-RAN split. When the RU can support dynamic split configuration, the method proceeds to814with determining one or more current operating parameters or conditions. These operating parameters or conditions may include base station system factors or fronthaul network factors such as measurements or determinations of base station loading (in particular the baseband controller or DU load), fronthaul bandwidth and/or traffic congestion, subcarrier spacing, RU processing capacity, reuse scaling considerations, UE distributions, and/or equipment interoperability. The method then proceeds to816with the split controller selecting a split configuration based on the determined one or more current operating parameters or conditions.

For example, in one embodiment the split controller may make a determination of current base station operating parameters that comprises DU and/or RU loading levels verses their respective processing capacities. If the DU is determined to be loaded above a predetermined threshold (such as above 50 percent processor loading, for example), then the processing capacity of the RU may be evaluated, and a DU/RU functional split configuration option selected that shifts the processing load off from the DU over to the RU, up to a predetermined threshold of RU processor loading. Similar decisions can be made based on base station operating parameters such as subcarrier spacing, where higher the subcarrier spacing, the more that processing can be shifted from the DU over to the RU due to smaller jitter buffer. Another approach would be for the split controller to decide the DU/RU functional split configuration based on operating conditions such as the distribution of UEs around RU. For example, if a number of UEs are concentrated closer in proximity to one RU than other RU served by the DU, then it makes sense for the DU to process downlink traffic using one of the delayed split, modulation split, or O-RAN split. Conversely, where UEs are spread relatively uniformly across the plurality of RUs served by the DU, then TBs can be more easily distributed to the RUs for processing using the early split option. Separate instances of the method800may also be performed to manage the DU/RU functional split configuration on a per-RU or per-BWP basis and independently for separate uplink and downlink channels.

FIG.9illustrates an example decision table900that may be utilized by a split controller210selecting a split configuration based on the determined current operating parameters or conditions. The decision criteria column includes each of the criteria considered by the split controller210when evaluating the current operating parameters or conditions. In alternate embodiments, the decision criteria may be listed in the order of importance, with the most significant criteria considered first. For each of the decision criteria, the decision table900then lists the various supported DU/RU functional splits in order of preference.

For example, if an RU106does not support the ability to dynamically control its functional split configuration (for example, if the RU is a 3rd Party RU or statically programmed only to utilize a standard O-RAN split), then RU support is the only relevant decision criteria to consider, and an O-RAN split is the first and only split option available for that RU106. If the RU106does support dynamic control of functional split configurations, then the other decision criteria may be considered. For example, if the current priority is to reduce latency of fronthaul traffic between the DU105and RU106, then per table900an early split is the functional split option of first choice, followed by delayed split, then modulation split, and then O-RAN split. That is, while the early split is the favored option to address the latency, current operating parameters or conditions may make the early split undesirable or unfeasible so that the second, third, or fourth choices need to instead be considered. In some embodiments, the various decision criteria may each be assigned a weighing factor so that the split controller210selects the split configuration by weighing each criteria and deciding the split based on the criteria that takes utmost importance (highest weight). In other embodiments, the split controller210applies the relative weighing factors and current operating parameters or conditions to an optimization algorithm to select a split option that best satisfies a combination of the various decision criteria. It should be appreciated that the split controller210may uses decision tables, such as decision table900, in this manner to select a split configuration based on the determined one or more current operating parameters or conditions for payloads for PDSCH, PBCH, PDCCH, PRACH, PUSCH, PUCCH, or other channels communicated over the fronthaul network125.

In order to better facilitate dynamic functional split configuration updates in real time, in some embodiments, the DU105and RU106(except for those RUs that do not support dynamic functional split configuration, for example) comprise the code and algorithms to perform the operational processes associated with each of the DU/RU functional split option pre-installed and then activate or deactivate which operational processes are currently executed based on the DU/RU functional split selected by the split controller210. For example, an RU106may have preinstalled the algorithms to perform the modulation310and compression312processes, but those processes would both be deactivated when a modulation split514or O-RAN split516is selected by the split controller and activated with an early split510or delayed split512is selected by the split controller. Similarly, the associated DU105may have preinstalled the algorithms to perform the modulation310and compression312processes, but those processes would both be activated when a modulation split514or O-RAN split516is selected by the split controller and deactivated with an early split510or delayed split512is selected by the split controller. Switching functional split options can therefore be promptly reconfigured with the base station remaining in service by simply activating or deactivating the processes at the DU and RU associated with the functional split selected by the split controller.

Moreover, in some embodiments, functional split reconfiguration actions can be discerned from analysis of the structure or content of the traffic being received from the fronthaul. For example, the split controller210function as implemented at the RU106analyses the downlink traffic being generated by the DU105as it is being received from the fronthaul network125. If the received traffic comprises unmodified transport blocks, then the split controller210function discerns that an early split510has been selected and activates the preinstalled the algorithms to perform the operational processes of the transmit chain300accordingly. If the received traffic instead comprises processed transport blocks up to but not including time domain processing318, then the split controller210function discerns that an O-RAN split516has been selected and activates the preinstalled the algorithms to perform the time domain processing318and deactivates the other operational processes of the transmit chain300accordingly. The split controller210function would similarly discern from the received traffic when a delayed split512or modulation split514has been selected and activate and deactivate the operational processes of the transmit chain300accordingly. In a similar way, in some embodiments the split controller210function as implemented at the DU105may analyze the uplink traffic being generated by the RU106as it is being received from the fronthaul network125. The split controller210function can discern from analysis of the structure or content of the traffic being received from the fronthaul whether an O-RAN split640, a late split650, or other functional split is in effect and activate and deactivate the operational processes of the receive chain400accordingly.

As mentioned above the compression performed at312may comprise standard O-RAN compression techniques, but in some embodiments may instead comprise an expanded bit depth compression technique to compress modulated symbols.FIGS.10and10Aprovide tables that illustrate multipliers, standard compression bit depth, and the expanded bit depth compression proposed by this disclosure for sample modulation orders of QPSK, 16 QAM, 64 QAM and 256 QAM. As should be appreciated, the modulation orders shown in table1000are for example purposes and other modulation orders may be utilized in conjunction with the embodiments disclosed herein. A QPSK modulated IQ symbol can take on one of four complex values and thus a compression realized by mapping each of those four potential complex values to a scalar value that can be represented in binary by two bits. Similarly, a 16 QAM modulated IQ symbol can take on one of sixteen complex values and a compression realized by mapping each of those sixteen potential complex values to a scalar value that can be represented in binary by four bits, and so forth for 64 QAM, 256 QAM, and higher order modulations. When a decoder receives the binary scalar value, the original complex modulated IQ symbol can be recreated via a table by looking up the complex modulated IQ symbol that corresponds to the received binary scalar value.

The expanded bit depth compression proposed by this disclosure instead maps the complex modulated IQ symbol to pairs of multipliers for each of the real (in-phase, I) and imaginary (quadrature, Q) components of the complex modulated IQ symbol, adding two bits to the binary scalar value (as compared to the standard compression) but eliminating the need for the lookup table because the original complex modulated IQ symbol can be directly computed and obtained from the received expanded bit binary scalar value. For example, in case of QPSK, standard O-RAN compression requires the modulation points to be represented using the scalar values 0,1,2,3 that each requires 2 bits in binary (0b00, 0b01, 0b10, 0b11). In contrast, with the expanded bit-depth scheme, 4 bits are utilized with the most significant byte (MSB) of the 4-bit word corresponding to the I component of the original complex modulated IQ symbol (in both sign and value), and the least significant byte (LSB) of the 4 bit word corresponding to the Q component of the original complex modulated IQ symbol (in both sign and value). Here for QPKS, the MSB either has a value of 01 corresponding to an I value of 1, or a value of 11 corresponding to an I value of −1. Similarly, the LSB either has a value of 01 corresponding to a Q value of 1, or a value of 11 corresponding to a Q value of −1. Each of the possible QPSK complex modulation points of 1+li, 1−li, −1+li, and −1−li can be represented in 4-bit binary as 0101, 0111, 1101 and 1111 allowing a decoder to reconstruct the original complex modulated IQ symbol directly without reference to a lookup table. The same scheme applies to the other modulation orders. For example, a 16 QAM complex modulated IQ symbol would be mapped to a 3-bit MSB for the I component and a 3-bit LSB for the Q component.

This expanded bit-depth compression method brings in a tradeoff between fronthaul traffic rate and implementation complexity. That said, the relative cost of the increase in fronthaul traffic rate caused by the use of two extra bits diminishes as the modulation order increases. In other words, while for QPSK the added two bits doubles the size of the compressed IQ symbol from 2 to 4 (an increase of 100%), for 256 QAM the added two bits doubles only increases the size of the compressed IQ symbol from 8 to 10 (an increase of only 25%). What is gained is a decrease in implementation complexity as look-up tables for each modulation order need not be stored and references by the decoding operation.

EXAMPLE EMBODIMENTS

Example 1 includes a system for base station functional split management for uplink fronthaul traffic, the system comprising: a baseband controller coupled to a plurality of radio units via a fronthaul network, wherein the plurality of radio units comprise a signal zone from which uplink signals are combined by a base station; a split controller configured to dynamically select and control a functional split of a respective uplink receive chain between the baseband controller and each of the plurality of radio units; wherein the functional split defines a demarcation point on the uplink receive chain prior to which processing operations are executed by a radio unit and after which processing operations are executed by the baseband controller; wherein the split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

Example 2 includes the system of Example 1, wherein each respective uplink receive chain comprises at least: a time domain processing operation; a channel estimation and interpolation operation; an equalization and antenna combining operation; a demodulation log-likelihood ratio (LLR) operation; and a channel decoding operation.

Example 3 includes the system of Example 2, wherein the time domain processing operation comprises one or both of a fast Fourier transform (FFT) operation or a cyclic prefix (CP) removal operations.

Example 4 includes the system of any of Examples 2-3, wherein the uplink receive chain further comprises an inverse discrete Fourier transform (IDFT) operation.

Example 5 includes the system of any of Examples 1-4, wherein the uplink receive chain is an uplink receive chain for a Physical Uplink Shared Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH).

Example 6 includes the system of any of Examples 1-5, wherein the split controller selects the functional split and the demarcation point based on an optimum signal-to-noise ratio (SNR) for a target block error rate (BLER) performance.

Example 7 includes the system of any of Examples 1-6, wherein the split controller selects the functional split and the demarcation point based on a combination of an optimum signal-to-noise ratio (SNR) and a fronthaul throughput.

Example 8 includes the system of any of Examples 1-7, wherein the split controller selects the functional split and the demarcation point based on measurements from a physical random access channel (PRACH), sounding reference signal (SRS) channel or a physical uplink control channel (PUCCH), in conjunction with how many radio units form the signal zone from which the uplink signals are being combined.

Example 9 includes the system of any of Examples 1-8, further comprising one or more communications channels between the plurality of radio units; wherein interference rejection combining (IRC) is performed at a first radio unit of the plurality of radio units based on information communicated via the one or more communications channels.

Example 10 includes the system of any of Examples 1-9, wherein based on the functional split selected by the split controller, minimum mean square error (MMSE) or Interference Rejection Combining (IRC) combining is applied to uplink radio frequency (RF) signals received at antennas at each of the plurality of radio units and equalized signal combining is executed at the baseband controller.

Example 11 includes the system of Example 10, wherein each of the plurality of radio units sends average noise variance per physical resource block (PRB) information to the baseband controller to aid MMSE combining.

Example 12 includes the system of any of Examples 1-11, wherein a functional split option of the plurality of functional split options comprises an open radio access network (O-RAN) split, wherein the demarcation point is defined on the uplink receive chain after time domain processing operations are performed at a radio unit and prior to channel estimation and equalization and antenna combining processing operations.

Example 13 includes the system of Example 12, wherein an IQ symbol output of the time domain processing operations are compressed to m bits before transmission over the fronthaul network.

Example 14 includes the system of any of Examples 12-13, wherein uplink IQ signals from multiple radio units are combined at the baseband controller.

Example 15 includes the system of any of Examples 12-14, wherein uplink IQ signals from multiple radio points are combined at the baseband controller using Interference Rejection Combining (IRC).

Example 16 includes the system of any of Examples 1-15, wherein a functional split option of the plurality of functional split options comprises an estimation split, wherein the demarcation point is defined on the uplink receive chain after channel estimation and interpolation operations are performed at a radio unit and prior to antenna combining processing operations.

Example 17 includes the system of Example 16, wherein an IQ symbol output of the channel estimation and interpolation operations are compressed to m bits before transmission over the fronthaul network.

Example 18 includes the system of any of Examples 1-17, wherein a functional split option of the plurality of functional split options comprises an equalization-combining split, wherein the demarcation point is defined on the uplink receive chain after equalizing and combining antennas operations are performed at a radio unit and prior to demodulation and log-likelihood ratio processing operations.

Example 19 includes the system of Example 18, wherein at the equalizing and combining antennas operations performed at the radio unit, the received uplink signals are equalized and combined before transmission on the fronthaul network.

Example 20 includes the system of any of Examples 18-19, wherein equalized symbols along with side information is sent over the fronthaul network for processing or multi RU combining at the baseband controller.

Example 21 includes the system of any of Examples 18-20, wherein each radio unit of the plurality of radio units performs Interference Rejection Combining (IRC) for its own antennas.

Example 22 includes the system of any of Examples 18-21, wherein equalized samples along averaged noise variance per antenna are transmitted as side information over the fronthaul network to achieve minimum mean square error (MMSE) equalization and achieve radio unit combining at the baseband controller.

Example 23 includes the system of any of Examples 18-22, wherein an IQ symbol output of the equalizing and combining antennas operation are compressed to n bits before transmission over the fronthaul network.

Example 24 includes the system of any of Examples 1-23, wherein a functional split option of the plurality of functional split options comprises an inverse discrete Fourier transform (IDFT) split, wherein the demarcation point is defined on the uplink receive chain after IDFT processing operations are performed at a radio unit and prior to demodulation and log-likelihood ratio processing operations.

Example 25 includes the system of Example 24, wherein an IQ symbol output of the IDFT processing operations are compressed to n bits before transmission over the fronthaul network.

Example 26 includes the system of any of Examples 1-25, wherein a functional split option of the plurality of functional split options comprises a demodulation split, wherein the demarcation point is defined on the uplink receive chain after demodulation log-likelihood ratio (LLR) operations are performed at a radio unit and prior to decoding processing operations.

Example 27 includes the system of Example 26, wherein demodulation is performed at the radio unit and resulting demodulated soft decisions per layer are transmitted over the fronthaul network to the baseband controller.

Example 28 includes the system of any of Examples 26-27, wherein soft decisions from multiple radio units are received and combined at the baseband controller prior to channel decoding to improve signal-to-noise (SNR) performance.

Example 29 includes the system of any of Examples 26-28, wherein a soft decisions output of the demodulation LLR operations is compressed to p bits per layer before transmission over the fronthaul network.

Example 30 includes the system of any of Examples 1-29, wherein a functional split option of the plurality of functional split options comprises a late split, wherein the demarcation point is defined on the uplink receive chain after decoding of the demodulated soft decision and resulting decoded bits are transmitted as a decoded transport block on the fronthaul network.

Example 31 includes the system of any of Examples 1-30, wherein the split controller individually selects the functional split for the respective uplink receive chain for each of the plurality of radio units.

Example 32 includes the system of any of Examples 1-31, wherein the fronthaul network is a switched Ethernet network.

Example 33 includes the system of any of Examples 1-32, wherein the fronthaul network is an Internet Protocol (IP) network.

Example 34 includes the system of any of Examples 1-33, wherein the base station comprises either a eNodeB base station or a gNodeB base station.

Example 35 includes the system of any of Examples 1-34, wherein the baseband controller comprises at least one central unit (CU) and at least one distributed unit (DU), wherein the plurality of radio units are coupled to the at least one DU by the fronthaul network.

Example 36 includes a method for base station functional split management for uplink fronthaul traffic, wherein a base station comprises a baseband controller coupled to a plurality of radio units via a fronthaul network, wherein the plurality of radio units comprise a signal zone from which uplink signals are combined by the base station, the method comprising: determining one or more current operating parameters or conditions; dynamically selecting, based on the one or more current operating parameters or conditions, a functional split of a respective uplink receive chain between the baseband controller and each of the plurality of radio units, wherein the functional split defines a demarcation point on the uplink receive chain prior to which processing operations are executed by a radio unit and after which processing operations are executed by the baseband controller; wherein a split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

Example 37 includes the method of Example 36, wherein the uplink receive chain is an uplink receive chain for a Physical Uplink Shared Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH).

Example 38 includes the method of any of Examples 36-37, wherein the split controller selects the functional split based on an optimum signal-to-noise ratio (SNR) for a target block error rate (BLER) performance.

Example 39 includes the method of any of Examples 36-38, wherein the split controller selects the functional split based on a combination of an optimum signal-to-noise ratio (SNR) and a fronthaul throughput.

Example 40 includes the method of any of Examples 36-39, wherein the split controller selects the functional split based on measurements from a physical random access channel (PRACH), sounding reference signal (SRS) channel or a physical uplink control channel (PUCCH), in conjunction with how many radio units form the signal zone from which the uplink signals are being combined.

Example 41 includes a system for base station functional split management for downlink fronthaul traffic, the system comprising: a baseband controller coupled to a plurality of radio units via a fronthaul network; a split controller configured to dynamically select and control a functional split of a respective downlink transmit chain between the baseband controller and each of the plurality of radio units; wherein the functional split defines a demarcation point on the downlink transmit chain prior to which processing operations are executed by the baseband controller and after which processing operations are executed by a radio unit; wherein the split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

Example 42 includes the system of Example 41, wherein the downlink transmit chain is a downlink transmit chain for a Physical Downlink Shared Channel (PDSCH), a Physical Broadcast Channel (PBCH), a Physical Downlink Control Channel (PDCCH), a Demodulation Reference Signal (DMRS), a Primary Secondary Signal (PSS), a Secondary Synchronization Signal (SSS) or a Channel State Information Reference Signal (CSI-RS).

Example 43 includes the system of any of Examples 41-42, wherein the split controller determines one or more operating parameters or conditions and selects the functional split and the demarcation point based on the one or more operating parameters or conditions.

Example 44 includes the system of Example 43, wherein the one or more operating parameters or conditions comprise system factor or fronthaul network factors that include at least one of: base station loading, fronthaul bandwidth, fronthaul traffic congestion, subcarrier spacing, radio unit processing capacity, reuse scaling, user equipment distribution within a cell, or equipment interoperability.

Example 45 includes the system of any of Examples 43-44, wherein the split controller determines and selects the functional split and the demarcation point based on a decision table comprising a plurality of decision criteria, wherein for each of the plurality of decision criteria the decision table associated one or more of the plurality of functional split options.

Example 46 includes the system of Example 45, wherein the decision criteria are each assigned a weighing factor, wherein the split controller selects a split configuration option based on the weighing factor.

Example 47 includes the system of any of Examples 45-46, wherein the decision criteria are each assigned a relative weighing factor, wherein the split controller applies the relative weighing factor and current operating parameters or conditions to an optimization algorithm to select the functional split.

Example 48 includes the system of any of Examples 41-47, wherein the split controller individually selects the functional split for the respective downlink transmit chain for each of the plurality of radio units.

Example 49 includes the system of any of Examples 41-48, wherein each respective downlink transmit chain comprises at least: a transport block (TB) Cyclic Redundancy Code (CRC) attachment operation; a code block concatenation and scrambling operation; a modulation operation; a layer mapping (LM) and precoding operation; a resource element mapping operation; and a time domain processing operation.

Example 50 includes the system of Example 49, wherein the modulation operation further includes a compression operation, wherein the compression operation applies an expanded bit-depth compression algorithm to complex modulated IQ symbols to generate a scalar value, wherein a first n bits are corresponding to an I component of an original complex modulated IQ symbol and a second n bits are corresponding to an Q component of the original complex modulated IQ symbol.

Example 51 includes the system of any of Examples 41-50, wherein a functional split option of the plurality of functional split options comprises an early split, wherein the demarcation point is defined at a start of the downlink transmit chain prior to scrambling, where an unprocessed transport block payload is forwarded from the baseband controller to a radio unit on the fronthaul network.

Example 52 includes the system of any of Examples 41-51, wherein a functional split option of the plurality of functional split options comprises a delayed split, wherein the demarcation point is defined on the downlink transmit chain after a scrambling operation is performed at the baseband controller and prior to a modulation processing operation performed at a radio unit.

Example 53 includes the system of any of Examples 41-52, wherein a functional split option of the plurality of functional split options comprises a modulation split, wherein the demarcation point is defined on the downlink transmit chain after modulation and compression operations are performed at the baseband controller and prior to a decompression, layer mapping (LM) and precoding processing operation processing's are performed at a radio unit.

Example 54 includes the system of any of Examples 41-53, wherein a functional split option of the plurality of functional split options comprises an open radio access network (O-RAN) split, wherein the demarcation point is defined on the downlink transmit chain after resource mapping performed at the baseband controller and prior to time domain processing operations performed at a radio unit.

Example 55 includes the system of any of Examples 41-54, wherein one or more of the plurality of radio units are configured to discern the functional split selected by the split controller based on an analysis of structure or content of traffic being received from the fronthaul network.

Example 56 includes the system of any of Examples 41-55, wherein the fronthaul network is a switched Ethernet network.

Example 57 includes the system of any of Examples 41-56, wherein the fronthaul network is an Internet Protocol (IP) network.

Example 58 includes the system of any of Examples 41-57, wherein the base station comprises either a eNodeB base station or a gNodeB base station.

Example 59 includes the system of any of Examples 41-58, wherein the baseband controller comprises at least one central unit (CU) and at least one distributed unit (DU), wherein the plurality of radio units are coupled to the at least one DU by the fronthaul network.

Example 60 includes a method for base station functional split management for downlink fronthaul traffic, wherein a base station comprises a baseband controller coupled to a plurality of radio units via a fronthaul network, the method comprising: determining one or more current operating parameters or conditions; dynamically selecting, based on the one or more current operating parameters or conditions, a functional split of a respective downlink transmit chain between the baseband controller and each of the plurality of radio units, wherein the functional split defines a demarcation point on the downlink transmit chain prior to which processing operations are executed by the baseband controller and after which processing operations are executed by a radio unit; wherein a split controller selects between a plurality of functional split options to dynamically control the functional split and the demarcation point.

Example 61 includes the method of Example 60, further comprising: determining, with the split controller, when the radio unit supports dynamic functional split configuration; and when the radio unit cannot support dynamic split configuration, processing transport blocks using an open radio access network (O-RAN) split.

Example 62 includes the method of any of Examples 60-61, wherein the downlink transmit chain is a downlink transmit chain for a Physical Downlink Shared Channel (PDSCH), a Physical Broadcast Channel (PBCH), or a Physical Downlink Control Channel (PDCCH).

Example 63 includes the method of any of Examples 60-62, wherein the split controller determines one or more operating parameters or conditions and selects the functional split and the demarcation point based on the one or more operating parameters or conditions.

Example 64 includes the method of Example 63, wherein the one or more operating parameters or conditions comprise system factor or fronthaul network factors that include at least one of: base station loading, fronthaul bandwidth, fronthaul traffic congestion, subcarrier spacing, radio unit processing capacity, reuse scaling, user equipment distribution within a cell, or equipment interoperability.

Example 65 includes the method of any of Examples 60-64, wherein a functional split option of the plurality of functional split options comprises an early split, wherein the demarcation point is defined at a start of the downlink transmit chain prior to scrambling, where an unprocessed transport block payload is forwarded from the baseband controller to a radio unit on the fronthaul network.

Example 66 includes the method of any of Examples 60-65, wherein a functional split option of the plurality of functional split options comprises a delayed split, wherein the demarcation point is defined on the downlink transmit chain after a scrambling operation is performed at the baseband controller and prior to a modulation processing operation performed at a radio unit.

Example 67 includes the method of any of Examples 60-66, wherein a functional split option of the plurality of functional split options comprises a modulation split, wherein the demarcation point is defined on the downlink transmit chain after modulation and compression operations are performed at the baseband controller and prior to a decompression, layer mapping (LM) and precoding processing operation processing's are performed at a radio unit.

Example 68 includes the method of any of Examples 60-67, wherein a functional split option of the plurality of functional split options comprises an open radio access network (O-RAN) split, wherein the demarcation point is defined on the downlink transmit chain after resource mapping performed at the baseband controller and prior to time domain processing operations performed at a radio unit.

Example 69 includes the method of any of Examples 60-68, further comprising: discerning, at one or more of the plurality of radio units, the functional split selected by the split controller based on an analysis of structure or content of traffic being received from the fronthaul network.

In various alternative embodiments, system and/or device elements, method steps, or example implementations described throughout this disclosure (such as any of the base stations, baseband controller, baseband unit, radio units, CU, CU-CP, CU-UP, DU. core network, split controller, MAC scheduler, device management system, or sub-parts thereof, for example) may be implemented at least in part using one or more computer systems, field programmable gate arrays (FPGAs), or similar devices comprising a processor coupled to a memory and executing code to realize those elements, processes, or examples, said code stored on a non-transient hardware data storage device. Therefore, other embodiments of the present disclosure may include elements comprising program instructions resident on computer readable media which when implemented by such computer systems, enable them to implement the embodiments described herein. As used herein, the term “computer readable media” refers to tangible memory storage devices having non-transient physical forms. Such non-transient physical forms may include computer memory devices, such as but not limited to punch cards, magnetic disk or tape, any optical data storage system, flash read only memory (ROM), non-volatile ROM, programmable ROM (PROM), erasable-programmable ROM (E-PROM), random access memory (RAM), or any other form of permanent, semi-permanent, or temporary memory storage system or device having a physical, tangible form. Program instructions include, but are not limited to computer-executable instructions executed by computer system processors and hardware description languages such as Very High Speed Integrated Circuit (VHSIC) Hardware Description Language (VHDL).

As used herein, cloud-based virtualized wireless base station related terms such as base stations, baseband controller, baseband unit, radio units, CU, CU-CP, CU-UP, DU. core network, split controller, MAC scheduler, device management system, fronthaul network, backhaul network, or sub-parts thereof, refer to non-generic elements as would recognized and understood by those of skill in the art of telecommunications and networks and are not used herein as nonce words or nonce terms for the purpose of invoking 35 USC 112 (f).