Method and apparatus for radio communication

Abstract

In an example embodiment, a system includes a chain of nodes coupled in series, the chain of nodes including a central processing node (CPN) and one or more radio communication nodes (RCNs). The CPN is coupled to a first RCN in the chain via a dielectric waveguide (DWG) link, and any other RCNs in the chain are connected in series from the first RCN in succession via other DWG links. The CPN generates outgoing radio carrier signals that propagate through the waveguide in a downstream direction of the chain for over-the-air (OTA) by a target RCN of the RCNs, while received radio carrier signals via OTA reception by each of the RCNs are received as incoming radio signals that propagate through the waveguide in an upstream direction of the chain for processing by the CPN. Advantages of the contemplated system include greatly simplified implementation of the RCNs with lower cost and power consumption. Furthermore, strategic placement of failover CPNs and DWG links provide for continued operation in the face of CPN or DWG link failure.

Description

TECHNICAL FIELD

[0001] The present invention relates to radio communication and use of radio communication nodes, e.g. with antenna processing units (APUs) supporting serial interconnection of central processing units (CPUs). BACKGROUND

[0002] The fifth generation (5G) mobile communication system promulgated by the Third Generation Partnership Project (3GPP) is designed to provide high quality of service (QoS). High QoS requires reliable radio connections between user equipment (UEs) and the network base stations serving them. Consider, for example, the deployment of an increasing number of wirelessly connected machine devices, some of which play safety-critical roles and require real-time communication with low latency and high reliability.

[0003] The phrase "cell-free massive multiple-input multiple-output (MIMO)" refers to a massive MIMO system in which base station antennas (sometimes referred to as access points (APUs)) are geographically dispersed. Each UE within the associated coverage area is surrounded by a serving APU, and there are no cell boundaries. The APUs are connected through a front-haul network to a central processing unit (CPU) that is responsible for processing data from each APU. This architecture promises an ultra-reliable network because, as a general proposition, any given UE can be accessed by more than one APU.

[0004] Other areas of interest in network development include the use of higher radio frequencies. The 5G specification introduces new frequency bands in the millimeter wave (mmW) range. See, e.g., "FR2" in 3GPP Technical Specification (TS) 38.104, which refers to the radio spectrum from 24.25 GHz to 52.6 GHz. The frequency bands for 6G are expected to be even higher, all the way up to hundreds of GHz. These high frequencies present challenges in radio propagation, and the cell-free massive MIMO architecture can complement the use of these higher frequencies for the radio carrier signals involved because the diversity of the distributed APUs makes it more likely that a given UE will be relatively close to one or more APUs. The architecture also addresses the problem of wall penetration in indoor deployment scenarios, but also presents many design and implementation challenges. SUMMARY

[0005] In an example embodiment, a radio communication system includes a chain of serially coupled nodes including a central processing node (CPN) and one or more radio communication nodes (RCNs). The CPN is coupled to a first RCN in the chain via a dielectric waveguide (DWG) link, and any other RCNs in the chain are serially connected from the first RCN in a serial fashion via other DWG links. The CPN generates outbound radio carrier signals that propagate through the waveguide in a downstream direction of the chain for OTA by a target RCN among the RCNs, while received radio carrier signals via OTA reception by individual ones of the RCNs propagate through the waveguide in an upstream direction of the chain for processing by the CPN as inbound radio signals. Advantages of the contemplated system include greatly simplified implementation of the RCNs with lower cost and power consumption. Moreover, the strategic placement of failover CPNs and DWG links in one or more embodiments of the system provides for continued operation in the face of CPN or DWG link failure.

[0006] In at least one embodiment, a radio communication system includes a CPN and two or more RCNs serially connected into a chain, where each serial link in the chain includes a DWG link, and each serial link has a downstream direction away from the CPN and an upstream direction toward the CPN. The CPN is configured to control individual ones of the RCNs to operate as base stations or relay stations.

[0007] Any given RCN in the chain operating as a base station (a) receives outbound radio carrier signals generated by the CPN and propagated along the downstream direction via the chain, and transmits the outbound radio carrier signals OTA as downlink radio carrier signals for reception by one or more UEs served by the base station; or (b) receives radio carrier signals OTA as uplink radio carrier signals sourced from one of the UEs served by the base station, and propagates the received radio carrier signals along the upstream direction via the chain for processing by the CPN.

[0008] Any given RCN in the chain operating as a relay station (a) receives inbound radio carrier signals propagated in the chain along the upstream direction, and propagates them to the next upstream hop in the chain, i.e., the next DWG link toward the CPN, or (b) receives outbound radio signals propagated in the chain along the downstream direction, and propagates them to the next downstream hop in the chain, i.e., the next DWG link away from the CPN.

[0009] Consider another example arrangement in which a radio communication system includes respective first and second RCN chains serially interconnected with a first CPN via associated DWG links, respective third and fourth RCN chains serially interconnected with a second CPN via associated DWG links, and respective fifth and sixth RCN chains serially interconnected with a third CPN via associated DWG links. Further, the system includes a failover element including a first failover DWG link coupling a terminal end of the second chain with a terminal end of the third chain, a second failover DWG link coupling a terminal end of the fourth chain with a terminal end of the fifth chain, a first failover CPN coupled with a terminal end of the first chain, and a second failover CPN coupled with a terminal end of the sixth chain. Accordingly, the supervisory device is configured to selectively activate the first and second failover CPNs and the first and second failover dielectric links to allow the first CPN or the first failover CPN to serve RCNs beyond the first failover DWG link, and to allow the third CPN or the second failover CPN to serve RCNs beyond the second failover DWG link.

[0010] In another example, an RCN includes a dielectric waveguide (DWG) interface operable to interconnect RCNs in a chain of RCNs interconnected via DWG links, with the chain anchored by a CPN. The RCN includes an upstream interface for coupling with an upstream DWG link, and includes a downstream interface for coupling with a downstream DWG. In a relay operation, the RCN couples an incoming radio carrier signal on its upstream interface to its downstream interface for waveguide transmission downstream along the chain to a next RCN, and couples an incoming radio carrier signal on its downstream interface to its upstream interface for waveguide transmission upstream to the CPN or to a next RCN. In a base station or "transceiver" operation, the RCN couples a received radio carrier signal received via over-the-air (OTA) into the upstream interface, and couples a radio carrier signal received via the upstream interface to its antenna circuitry for OTA transmission.

[0011] In more detail, an RCN in one or more embodiments includes an antenna circuit and a DWG interface. The antenna circuit is configured for OTA transmission of radio carrier signals via an antenna array and for over-the-air reception of radio carrier signals via the antenna array.

[0012] Accordingly, the DWG interface is coupled to the antenna circuitry and configured for series interconnection of the RCN via the DWG links. To this end, the DWG interface includes a first coupling circuit for transmitting radio carrier signals into the first DWG and receiving radio carrier signals from the first dielectric waveguide, and further includes a second coupling circuit for transmitting radio carrier signals into the second DWG and receiving radio carrier signals from the second dielectric waveguide.

[0013] The control circuitry of the RCN configures the RCN for either a relay operation or a base station operation. In the base station operation, the received radio carrier signals transmitted via OTA by the antenna circuitry are coupled into the DWG interface and transmitted into at least one of the first DWG and the second DWG, while the radio carrier signals received by the DWG interface are coupled into the antenna circuitry for over-the-air transmission. In the relay operation, the radio carrier signals received from the DWG via the first coupling circuit are coupled into the second coupling circuit (94) and transmitted into the second DWG, and the radio carrier signals received from the second DWG via the second coupling circuit are coupled into the first coupling circuit and transmitted into the first DWG.

[0014] Yet another example relates to a method of operating an RCN positioned as one of a series link of RCNs, where the series link includes interconnecting DWGs (referred to as series links or hops) and serially interconnects the RCNs to a CPN. The CPN anchors the series link and transmits out-bound radio carrier signals via the series link for over-the-air transmission by a particular RCN of the RCNs and receives in-bound radio carrier signals via the series link for processing by the CPN.

[0015] With reference to the CPN and RCN arrangement just described above, one embodiment of the method includes, in the case where the out-bound radio carrier signals are targeted to UEs served by the RCN, the RCN receiving the out-bound radio carrier signals travelling in the outbound direction along the series link and performing OTA transmission of the out-bound radio carrier signals, or in the case where the out-bound radio carrier signals are not targeted to UEs served by the RCN, propagating the out-bound radio carrier signals along the next outbound hop of the series link. Of course, there can be certain radio carrier signals that are both propagated in the series link and OTA transmitted by the RCN, such as out-bound radio carrier signals intended for broadcast by some or all of the RCNs in the chain.

[0016] The method also includes the RNC receiving an inbound radio carrier signal travelling in an inbound direction along the serial link and propagating the inbound radio carrier signal along a next inbound hop of the serial link; and receiving a radio carrier signal as an over-the-air transmission from a UE served by the radio communication node and propagating the received radio carrier signal as an inbound radio carrier signal along a next inbound hop of the serial link. Of course, such operations can be performed at different times and the method can include operating in a time-division duplex (TDD) manner such that, at least for the same DWG, OTA reception and transmission by the RCN are mutually exclusive, and / or such that RCN propagation of inbound radio carrier signals is mutually exclusive with propagation of outbound radio carrier signals.

[0017] The RCNs are also referred to as “antenna processing units” or APUs to denote their simplified structure and to emphasize that, while the APUs can provide transmit and / or receive beamforming, the CPN provides processing for all radio carrier signals processed by the APUs. For example, the CPN provides modulation and upconversion to generate outbound radio carrier signals and provides downconversion and demodulation for inbound radio carrier signals. Thus, the CPN (also referred to as a central processing unit or CPU) can be referred to as a distributed base station (BS).

[0018] An example distributed BS includes a chain that includes a CPU and one or more APUs, where the CPU is connected to a first one of the APUs via a first DWG link. To the extent that the chain includes a second APU, a second DWG link interconnects the first APU with the second APU, and any other APUs are connected in series using respective other DWG links. Each DWG link includes at least one DWG, which can be referred to as a “slice”. Of course, each DWG link can include two or more DGWs in parallel, e.g., for increased capacity and / or for carrying differently polarized radio carrier signals.

[0019] In example implementations that keep waveguide dimensions feasible, the DWGs accommodate high operating frequencies (e.g., 90 GHz and above) and exhibit reasonable insertion loss. Also, as an overall characteristic of the envisioned radio communication system and its constituent elements, e.g., its included CPUs and APUs, radio carrier signals that are OTA transmitted or OTA received by an APU in the chain have the same operating frequency and modulation as corresponding outbound and inbound radio carrier signals that are DWG propagated in the chain. That is, as previously mentioned, the CPU provides radio carrier signal processing, e.g., frequency upconversion and modulation of outbound radio carrier signals input into the chain, for DWG propagation to RCNs that are targets of OTA transmission of these outbound radio carrier signals.

[0020] The APUs can be in a standby, repeater mode, or a transceiver mode, with the latter mode also being referred to as a base station mode. In at least some cases or at least in some arrangements, only one of the APUs connected in series at a time is in the transceiver mode. As one notable exception, all APUs can transmit broadcast channel signals at the same time.

[0021] Of course, the present application is not limited to the features and advantages summarized above. Additional features and advantages will be realized upon reading the following detailed description, and viewing the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a block diagram of one embodiment of a wireless communication network.

[0023] Figure 2 is a block diagram of an example arrangement of a serial chain anchored by a central processing unit, where each chain includes a series of sets of radio communication nodes controlled by the central processing unit, and where dielectric waveguides (DWGs) provide serial interconnection.

[0024] Figure 3 is a block diagram of one embodiment of a radio communication node for use in a chain.

[0025] Figure 4 is a block diagram of one embodiment of a central processing unit for use in a chain.

[0026] Figure 5 is a schematic diagram of one embodiment of radio frequency circuitry within a radio communication node.

[0027] Figure 6 is a block diagram illustrating one embodiment of a system including multiple chains.

[0028] Figure 7 is a block diagram illustrating another embodiment of a system including multiple chains, with features providing failover operation and / or increased system capacity.

[0029] Figure 8 is a block diagram illustrating one embodiment of a user equipment (UE).

[0030] Figure 9 is a logic flow diagram illustrating one embodiment of a method operated by a radio communication node in a chain.

[0031] Figure 10 is a block diagram of another embodiment of a radio communication node.

[0032] Figure 11 is a block diagram of one embodiment of a DWG interface configured for use by a radio communication node in a chain. DETAILED DESCRIPTION

[0033] Figure 1 is a block diagram of one embodiment of a wireless communication network 10 ("network 10") configured to provide one or more types of communication services to user equipment (UE) 12. For example, the network 10 operates as an access network that provides access to one or more external networks (14) (e.g., the Internet).

[0034] While Figure 1 Five UEs 12-1 through 12-5 are depicted, but this depiction is not limiting as the number of UEs 12 connected with the network 10 varies over time. As with the UEs 12, other figures in the figures can describe the same or at least substantially similar elements for the purpose of discussion using suffixed figure references. However, for the sake of clarity, this specification only refers to the suffixes as necessary. Thus, a figure reference "12" without a suffix can be used to refer to a given UE in the singular or to a given UE in the plural. The same applies to other figure references that are depicted with a suffix in any figure. Figure 1 and other figures in the figures can describe the same or at least substantially similar elements for the purpose of discussion using suffixed figure references. However, for the sake of clarity, this specification only refers to the suffixes as necessary. Thus, a figure reference "12" without a suffix can be used to refer to a given UE in the singular or to a given UE in the plural. The same applies to other figure references that are depicted with a suffix in any figure.

[0035] The term "UE" essentially encompasses any type of wireless communication device configured to utilize the network 10 (i.e., to communicate via a wireless attachment with the network 10). Example types or categories of UEs include a smartphone, a feature phone, a laptop computer, a tablet computer, or other personal computing device. Other examples include a machine type communication (MTC) device or an Internet of Things (IoT) device, e.g., a sensor and a controller. The UEs 12 served by the network 10 can be of the same type or a mix of types, and this mix can vary over time. One or more of the UEs 12 served by the network 10 can be embedded, e.g., in a vehicle, and one or more of the UEs 12 can be fixed. For example, the network 10 can be a room interior deployment for UEs 12 within a building, or can be outdoors in an urban area with pedestrian and vehicular traffic.

[0036] The network 10 in the example embodiments is configured in accordance with Third Generation Partnership Project (3GPP) specifications. In at least one embodiment, the network 10 is a Fifth Generation (5G) New Radio (NR) network in accordance with the corresponding 3GPP specifications. See the specifications referred to as 3GPP Release 15 and later releases. However, the architecture of the network 10 has broader applicability than 5G NR deployments, and 5G NR is just one example.

[0037] Different“parts” of the network 10 include a radio access network (RAN) part 16 (also referred to as RAN 16) and a core network (CN) part 18 (also referred to as CN 18). While not necessarily closely related to radio operations of interest herein, the CN 18 provides authentication, mobility management, and external network interface functionality to support providing communication services to the UEs 12, while the RAN 16 provides the air interface over which the UEs 12“connect” to the network 10.

[0038] Example details of the RAN 16 include a central processing unit (CPU) 20 and one or more antenna processing units (APUs) 22, e.g., APU 22-1 through 22-5. One characteristic arrangement contemplated herein is that the CPU 20 and the one or more APUs 22 form“chains” 26 of serially interconnected or interconnected entities. In Figure 1 In particular, the CPU 20 anchors two different chains, namely a first chain 26-1 including the APUs 22-1, 22-2, and 22-3 in series and a second chain 26-2 including the APUs 22-4 and 22-5 in series.

[0039] The entities making up each chain 26 are interconnected via dielectric waveguide (DWG) links 28. For example, for the chain 26-1, the CPU 20 is coupled to the APU 22-1 via a first DWG link 28-1, the APU 22-1 is coupled to the APU 22-2 via a second DWG link 28-2, and the APU 22-2 is coupled to the APU 22-3 via a third DWG link 28-3. For the chain 26-2, the CPU 20 is coupled to the APU 22-4 via a first DWG link 28-4, and the APU 22-4 is coupled to the APU 22-5 via a second DWG link 28-5.

[0040] Each chain 26 has a directionality, with the direction away from the CPU 20 being referred to as the“downstream” direction and the direction toward the CPU 20 being referred to as the“upstream” direction. Using this nomenclature, the CPU 20 generates“outbound” radio carrier signals and propagates them along the downstream direction into the chain 26 for one or more of the APUs 22 in that chain 26 to transmit over the air (OTA). Conversely, radio carrier signals received via OTA by a given one of the APUs 22 are propagated along the upstream direction in the chain 26 for delivery to the CPU 20 for processing (e.g., down-conversion and demodulation).

[0041] It can be said that the propagation of the radio carrier signal in the chain 26 refers to the DWG transfer of the radio carrier signal over one or more successive "hops" or "links" in the chain 26. Each DWG link 28 in the chain constitutes a serial hop or link. The radio carrier signals that propagate in the chain 26 can also be referred to as "guided" radio carrier signals or "distributed" radio carrier signals to emphasize that they are transferred via DWG. With this in mind, one way to understand the operation of the chain 26 is that the CPU 20 generates an outbound radio carrier signal that is then propagated downstream in the chain 26 as needed for OTA transmission by one or more of the APUs 22 in the chain 26. In the opposite direction, a radio carrier signal received via OTA reception by a given APU 22 is propagated upstream in the chain 26 to the CPU 20.

[0042] Consider an example case in which the APU 22-1 in the chain 26-1 operates as a serving base station for the UE 12-1 and the CPU 20 generates a radio carrier signal that carries user traffic for the UE 12-1. The CPU 20 has a DWG interface that couples it to one end of the DWG link 28-1, and it uses this interface to propagate the generated radio carrier signal into the DWG link 28-1 as an outbound radio carrier signal for the UE 12-1. Next, the APU 22-1 includes an "upstream" DWG interface that couples it to the other end of the DWG link 28-1, and it receives the outbound radio carrier signal via its upstream DWG interface. Because the outbound radio carrier signal is targeted for the UE 12 served by the APU 22-1, the APU 22-1 performs OTA transmission of the radio outbound carrier signal.

[0043] Consider a similar example, but the outbound radio carrier signal is targeted for the UE 12-4 served by the APU 22-3. In this case, the APU 22-1 propagates the outbound radio carrier signal to the next hop in the chain 26-1, which is the DWG link 28-2 that couples the APU 22-1 to the APU 22-2. Next, the APU 22-2 propagates the outbound radio carrier signal to the next hop in the chain 26-1, which is the DWG link 28-3 that couples the APU 22-2 to the APU 22-3.

[0044] Now consider the inbound case, in which a given APU 22 within the chain 26 receives an OTA transmission from a UE 12 it serves. That is, the given APU 22 receives an uplink radio carrier signal from a UE 12. The given APU 22 couples the received uplink radio carrier signal on its upstream side - facing the CPU 20 - into the DWG link 28 for propagation in the chain 26 in the upstream direction as an inbound radio carrier signal for the CPU 20. Any intervening APUs 22 in the upstream direction between the given APU 22 and the CPU 20 perform respective next-hop propagation of the inbound radio carrier signal toward the CPU 20.

[0045] Thus, each APU 22 can transmit and receive via its DWG interface for propagating radio carrier signals within the chain 26 - i.e., waveguide transmission in either the downstream direction or the upstream direction along the chain 26. Moreover, each APU 22 includes or is associated with an antenna array 24 for OTA transmission of radio carrier signals (referred to as downlink (DL) transmission) and OTA reception of radio carrier signals (referred to as uplink (UL) reception).

[0046] All APU operations can be managed and controlled by the CPU 20, e.g., by the CPU 20 allocating control signaling in the chain 26 for the included APUs 22. In one or more embodiments, each APU 22 operates in a TDD manner such that it performs OTA reception mutually exclusive of OTA transmission, and for one DWG it is coupled with, it performs DWG reception mutually exclusive of DWG transmission.

[0047] Each DWG link 28 includes at least one DWG - i.e., the term "DWG link" as used herein refers to at least one dielectric waveguide. In at least one embodiment, each DWG link 28 includes a pair of parallel DWGs, each DWG in the parallel pair dedicated to a different radio carrier signal polarization. In relation to this example arrangement, Figure 1 DWG link 28-1 is an upstream link with respect to APU 22-1 and it includes a pair of parallel DWGs, while DWG link 28-2 is a downstream link with respect to APU 22-1 and it includes a pair of parallel DWGs. Of course, for APU 22-2, DWG link 28-2 is an upstream link, while DWG link 28-3 is a downstream link for APU 22-2.

[0048] The use of two or more parallel DWGs in each DWG link 28 allows separate radio carrier signals to be simultaneously propagated on the DWG link 28, e.g., for different polarizations and / or greater signal capacity in the chain 26. For example, in relation to the example arrangement of FIG. 1, Figure 1In particular, consider the case where each DWG link 28 in the chain 26-1 includes a single DWG for each polarization in use. This means that, at least in a TDD implementation, a series of DWG sets are available throughout the chain 26-1 for transmitting or receiving radio carrier signals of the involved polarizations.

[0049] In at least one arrangement, the DWG links 28 within the chain 26 include 2xN parallel DWGs, with the APU 22 in the chain 26 being staggered and every Nth APU 22 being connected to the same pair of DWGs. Moreover, by terminating the chain 26 at each end with a CPU 20, this arrangement will obtain capacity increase and increased robustness. For example, if needed, one of the terminating CPUs 20 can take over the other using the same set of series-connected DWGs, or for each of the CPUs 20, the DWG links 28 in the chain 26 can have a respective set of series-connected DWGs such that one of the CPUs 20 acts as a master CPU on one of the sets of series-connected DWGs, while the other CPU 20 acts as a master CPU on the other set of series-connected DWGs. Of course, the APU 22 will be configured to support such operation.

[0050] By TDD operation of the CPUs 20, APU 22, and DGW links 28 in a chain 26-1, conveying radio carrier signals along the chain 26-1 in a downstream direction is mutually exclusive with conveying them along the upstream direction. Thus, all of the UEs 12 served by the chain 26-1“share” radio carrier signal bandwidth in time, serving only one UE 12 at a time. To vary this, for each polarization in use, the chain 26-1 can include more than one DWG in each DWG link 28, such that a first series of DWG sets in the chain 26-1 can be used to serve a given UE 12 at a given time instant, while a second DWG set in the chain 26-1, parallel to the first set, can be used to simultaneously serve another given UE 12.

[0051] However, whether each of the DWG links 28 forming a series of DWG sets includes a single DWG or two or more parallel DWGs, the DWG-based connection arrangement provides significant advantages. For example, using a digital interface for the serial interconnections in the chain 26 would incur serious problems with respect to power consumption and complexity of the serial interconnections and the APU 22, particularly at very high bit rates for traffic exchanged with the UEs 12 served by the network 10. At a minimum, use of a digital interface would require each APU 22 to include a corresponding analog-to-digital converter and digital-to-analog converter.

[0052] Furthermore, as noted, the APU 22s contemplated herein do not perform any modulation, demodulation, or frequency shifting, meaning that they transmit the radio carrier signals of the OTAs identically to the radio carrier signals they receive from the CPU 20 via the downstream propagation in the chain 26, of course, subject to any transmit beamforming applied by the APU 22. Similarly, the APU 22 can perform receive beamforming, but beyond that, the radio carrier signals of the OTAs received into the APU 22 are identical to the carrier radio signals that the APU 22 propagates in the upstream direction as the inbound radio signals of the CPU 20.

[0053] As a further advantageous simplification used in one or more embodiments of the APU 22, the DWG interface included in the APU 22 operates in a TDD fashion with respect to each DWG included in the corresponding DWG link 28-1. That is, for a single DWG, the DWG interface transmits and receives on an exclusive basis. This arrangement reduces complexity, e.g., the need for duplexers and other frequency multiplexing circuitry. And, as noted, the APU 22 does not perform frequency translation or frequency shifting on the radio carrier signals it handles.

[0054] Figure 2 An example system contemplated herein is shown. Here the CPU 20 is connected to two chains of serially interconnected APU 22s. Each chain or serial link consists of several APU 22s connected in series. The DWGs carry the radio carrier signals between the APU 22s. For high frequency radio carrier signals, the DWGs used to implement the DWG links 28 need only have a cross-sectional area of a few square millimeters, and are inexpensive and flexible, as well as having manageable losses, e.g., less than 3 dB per meter. And, as will be detailed later, the DWG interfaces used by the CPU 20 and the APU 22s can radiate their output radio carrier signals non-contactingly into the respective DWGs.

[0055] In each serially connected APU 22, the radio carrier signals incoming to the APU 22 via its DWG interface are amplified by us to restore the signal level. The amplification adds noise and distortion, and accordingly, the maximum practical length of the chain 26 is a function of the losses in the DWG links 28 as well as the APU noise figure and distortion. The target modulation and system bandwidths also limit the maximum length.

[0056] Figure 3 An APU 22 in an example embodiment is depicted. The APU 22 includes two sides in a functional sense, which are labeled in the figure as SIDE 1 and SIDE 2. One is the upstream side facing the CPU 20, which controls the chain 26 in which the APU 22 runs, while the other side is the downstream side facing away from the CPU 20.

[0057] The APU 22 includes "A" elements for a first radio carrier signal polarization (e.g., horizontal polarization) and "B" elements for a second radio carrier signal polarization (e.g., vertical polarization). Correspondingly, the antenna array 24 includes a small antenna matrix for each polarization. Only the A matrix is visible in the figure. Each antenna matrix provides beamforming gain and thus improves the link budget between the APU 22 and the UEs 12 it serves, while improving the interference situation in implementations where multiple strands 26 use the same radio carrier frequency. For a 100 GHz radio carrier signal, an example matrix size is 6 mm x 12 mm, with the antenna elements 54 spaced apart by λ / 2 (1.5 mm).

[0058] The example APU 22 also includes antenna circuitry 40 that interfaces with the antenna array 24, dielectric waveguide interfaces 42, and control circuitry 44 that can exchange control signaling on the upstream side and the downstream side of the APU 22. For example, the CPU 20 can output control signaling for the APUs 22 in a strand 26, and each APU 22 in the strand can transfer some or all of this signaling to the next APU 22 in the strand. The signaling can be common to the A and B portions of the APU 22, or it can be separate for the A and B portions, e.g., coordinated but separate signaling for the A and B radio carrier signal polarizations handled by the APU 22. Figure 3 This is shown where 46-1A represents upstream side control signaling associated with the A portion of the APU 22, 46-1B represents upstream side control signaling associated with the B portion of the APU 22, 46-2A represents downstream side control signaling associated with the A portion of the APU 22, and 46-2B represents downstream side control signaling associated with the B portion of the APU 22. Of course, this example is not limiting, and other control signaling arrangements can be envisioned.

[0059] In a similar A / B fashion, the DWG interfaces 42 of the APU 22 connect to two DWGs in each direction. That is, on the SIDE 1 of the APU 22, the DWG interfaces 42 provide DWG coupling for the two DWGs that make up the SIDE-1 DWG link 28-1. These two SIDE-1 DWGs are denoted as 30-1A and 30-1B corresponding to the A and B portions of the APU 22, respectively. Likewise, the DWG interfaces 42 provide DWG coupling for the two DWGs 30 that make up the SIDE-2 DWG link 28-2. These two SIDE-2 DWGs are denoted as 30-2A and 30-2B corresponding to the A and B portions of the APU 22, respectively.

[0060] DWG 30-1A on SIDE 1 "maps" to DWG 30-2A on SIDE 2, meaning that, in a relay operation, APU 22 couples radio carrier signals incoming to APU 22 from DWG 30-1A to DWG 30-2A, and vice versa. The same lateral side mapping applies to DWGs 30-1B and 30-2B. In at least one embodiment, DWG pair 30-1A / 30-2A handles a first radio carrier signal polarization (e.g., horizontal polarization), and DWG pair 30-1B / 30-2B handles a second radio carrier signal polarization (e.g., vertical polarization). For TDD operation, only one DWG per polarization is needed on either side of APU 22.

[0061] Assuming SIDE 1 is the upstream side of APU 22 (in downlink (DL) operation, also referred to as outbound operation), DWGs 30-1A and 30-1B carry corresponding outbound radio carrier signals of "A" and "B" polarizations originating from CPU 20 and propagating in chain 26 toward APU 22. If APU 22 is used as a relay station, its DWG interface 42 couples these outbound radio signals to SIDE 2 of APU 22, into DWGs 30-2A and 30-2B, for the next APU 22 in chain 26. Conversely, in base station or transceiver mode, APU 22's DWG interface 42 couples outbound radio carrier signals incoming on DWGs 30-1A and 30-1B into antenna circuitry 40 for OTA transmission from A-antenna matrix and B-antenna matrix in antenna array 24. Figure 3

[0062] Again, assuming SIDE 1 is the upstream side of APU 22 (in uplink (UL) operation, also referred to as inbound operation), APU 22's relay station operation involves APU 22 receiving inbound radio carrier signals on its downstream side (SIDE 2), namely on DWGs 30-2A and 30-2B, where these signals are received via OTA reception by another APU 22 that is downstream in chain 26. APU 22 couples these inbound signals into SIDE-1 DWGs 30-1A and 30-1B for propagation toward CPU 20. For base station mode UL operation, APU 22 receives UL radio carrier signals from UE 12 and couples them into its SIDE 1 DWG interface for propagation toward CPU 20 as inbound radio carrier signals.

[0063] Another point worth emphasizing is that, Figure 3 ​The A / B separation shown in the middle is helpful for discussion, but they are not meant to suggest a limitation on how the APU 22 is implemented in terms of multiplexing. At least some aspects can be integrated.

[0064] Figure 3 Other example elements shown in the APU 22 include a signaling interface 48 of the control circuit 44, which can include two respective control interfaces 50, with interface 50-1 for control signaling connections on the upstream side of the APU 22, and interface 50-2 for control signaling connections on the downstream side of the APU 22. For example, the CPU 20 generates control signaling for controlling the APU 22 included in the chain 26, e.g., TDD-related control signaling that determines the relay station operation and base station operation of the respective APU 22 in the chain 26. Such signaling can flow via a serial control signaling link between the CPU 20 and successive APU 22 in the chain 26, with the APU 22 closest to the CPU 20 receiving the control signaling directly from the CPU 20 and passing it all or in part to the next APU 22, and so on.

[0065] To this end, in one or more embodiments, the control circuit 44 includes one or more microprocessors, digital signal processors (DSPs), field programmable gate arrays (FPGAs), or application specific integrated circuits (ASICs), or any combination thereof. The control circuit 44 can include or be associated with a memory or other computer readable medium, and can operate according to execution of stored computer program instructions.

[0066] In at least one embodiment, the DWG 30 including the DWG link 28 has a conductive exterior 52 that provides an electrical connection for exchanging control signaling between the CPU 20 and adjacent APU 22, and between adjacent APU 22. The conductive exterior 52 includes, for example, a metallic coating or conductive sheath. In other embodiments, a dedicated wired connection independent of the DWG link 28 electrically interconnects the CPU 20 and the APU 22. In either case, the control signaling includes, for example, TDD control signaling and mode control signaling, according to which the CPU 20 determines which APU 22 transmits or receives OTA radio carrier signals at what times. The control signaling thus provides for operation of the APU 22 as a distributed antenna system, with the CPU 20 scheduling transmission and / or reception of user traffic from respective UEs 12 served by the chain 26 via respective ones of the APU 22 in the chain 26.

[0067] Each APU 22 can also include, or be associated with, a power management unit (PMU) 56. For example, the PMU 56 provides operating power for the antenna circuitry 40, the DWG interface 42, and the control circuitry 44. In at least some embodiments, the PMU 56 is controllable by the CPU 20 via control signaling. In addition to the conductive exterior 52 of the DWG in the DWG link 28 carrying control signaling, the conductive exterior 52 can also be used to provide operating power, e.g., a DC voltage supply down the chain 26 of the APU 22.

[0068] In a Power over Ethernet (POE) example, a 48V DC power signal is carried via the conductive coating 52 included in the respective DWG link 28. However, lower operating voltages can be used, e.g., to facilitate full monolithic integration of the circuitry including each APU 22. To some extent, the voltage drop created across the continuous interconnect used to carry control signaling down the chain 26 of the APU 22 can dictate the voltage level of the DC power signal, and the PMU 56 of each APU 22 can include a DC / DC converter as needed to provide the particular operating voltage required within the APU 22.

[0069] While carrying control signaling on the power feed can be advantageous in terms of reduced complexity and part count, this arrangement should be understood as a non-limiting example of a control signaling interconnect. More broadly, the control signaling arrangement can be implemented as a parallel, low frequency serial peripheral interface (SPI), with the CPU 20 outputting control signaling for individual ones of the APUs 22 via the SPI.

[0070] For example, each APU 22 has a unique identifier that allows the CPU 20 to identify which APU 22 is the target of particular control signaling. For example, an application specific integrated circuit (ASIC) or other integrated circuit used within each APU 22 can be fused with a unique identifier that fixes the APU identity. Dynamic or configurable identities can also be used in one or more embodiments. An APU 22 that receives control signaling that is not targeted for it will pass it in a downstream direction along the next control signaling hop in the chain 26. Likewise, upstream control signaling will be passed from APU 22 to APU 22 in the chain 26 as needed to reach the CPU 20.

[0071] As noted above, the CPU 20 uses the control signaling to, among other things, control the state of each APU 22 in the chain 26, etc. Here, possible states can be a relay mode, a base station mode, and a standby mode that are set under control of the CPU 20.

[0072] Figure 4An example arrangement of the CPU 20 in one or more embodiments is shown. The CPU 20 includes a DWG interface 60 that includes receive circuitry 62 and transmit circuitry 64 for coupling to the DWG, including the DWG link 28 in the first APU 22 of its chain 26 of APUs 22 controlled by the CPU 20. In at least one embodiment, the DWG interface 60 of the CPU 20 uses an antenna 66 to transmit outbound radio carrier signals into the associated DWG link 28 and to receive inbound radio carrier signals from the associated DWG link 28. The antenna 66 can be positioned for transverse feeding into the associated DWG link 28, and the same arrangement can be implemented in each APU 22 for coupling with their respective upstream and downstream DWG links 28.

[0073] The CPU 20 also includes processing circuitry 68 that includes baseband radio processing circuitry 70 for baseband processing of outbound and inbound signals corresponding to outbound and inbound radio carrier signals. The CPU 20 also includes control circuitry 72 configured for controlling operation of the CPU 20 and for controlling one or more chains 26 of APUs 22 coupled with the CPU 20. To this end, the control circuitry 72 is associated with one or more control signaling interfaces 74 (e.g., SPI circuitry). The control circuitry 72 or the processing circuitry 68 can also be generally associated with one or more network interfaces 84, e.g., that support backhaul connections carrying user traffic and related network control signaling between the CPU 20 and one or more supporting nodes in the CN 18.

[0074] In one or more embodiments, the processing circuitry 68 includes or is associated with a storage 76, e.g., for storing configuration data 78 associated with operation of the CPU 20 and / or one or more computer programs (the figure's "CP") including program instructions whose execution by one or more microprocessors or other types of digital processors configures such processor as the processing circuitry 68. That is, the processing circuitry 68 can be a fixed circuit or a programmed circuit, and in at least one embodiment, the processing circuitry 68 is implemented at least in part by one or more microprocessors that are specifically adapted according to their execution of computer program instructions stored in the storage 76.

[0075] Accordingly, storage 76 provides at least temporary storage of computer programs (CP) 80, and can also provide working memory for program execution. Broadly, storage 76 includes one or more types of computer-readable media, non-limiting examples of which include any one or more of SRAM, DRAM, NVRAM, FLASH, EEPROM, and solid-state disk (SSD).

[0076] CPU 20 also includes radio frequency circuitry 82 associated with baseband radio processing circuitry 70 and DWG interface 60. In cooperation with baseband radio processing circuitry 70, CPU 20 uses radio frequency circuitry 82 to generate outbound radio carrier signals for output via DWG interface 60. Likewise, CPU 20 uses radio frequency circuitry 82 to process inbound radio carrier signals received via DWG interface 60. In this regard, CPU 20 can be understood to provide all modulation and up-conversion processing for outbound radio carrier signals transmitted in chain 26 of APU 22, and all demodulation and down-conversion processing for inbound radio carrier signals transmitted in chain 26 of APU 22.

[0077] Figure 5 An example embodiment of APU 22 is shown, focusing on an example implementation of DWG interface 42 and antenna circuitry 40. Antenna circuitry 40 includes first radio frequency circuitry 90, and DWG interface 42 includes second radio frequency circuitry 92.

[0078] In an example case, antenna array 24 includes sixteen antenna elements for transmit and / or receive beamforming, and first radio frequency circuitry 90 includes a corresponding radio frequency circuit block 96 for each antenna element of antenna array 24. Each block 96 includes a switch 100, a power amplifier (PA) 102, a low noise amplifier (LNA) 104, a switch 106, a beamforming circuit element 108, and a splitter / combiner (S / C) 110.

[0079] Second radio frequency circuitry 92 includes respective DWG coupling circuitry 94-1 and 94-2. Each DWG coupling circuitry 94 provides transmit / receive coupling into DWG 30 via an associated antenna 98. To the extent that APU 22 supports more than one DWG 30 per DWG link 28, each DWG 30 will have DWG coupling circuitry 94. Temporarily returning to Figure 3 , the depicted APU 22 will include two DWG coupling circuitry 94 on SIDE 1, one for the SIDE-1A connection and one for the SIDE-1B connection, and two DWG coupling circuitry 94 on SIDE 2, one for the SIDE-2A connection and one for the SIDE-2B connection.

[0080] Further, asFigure 5 As seen in the middle, each DWG coupling circuit 94 on one side of the APU 22 is paired (coupled) with a corresponding DWG coupling circuit 94 on the other side of the APU 22. That is, each DWG coupling circuit 94 on the upstream side of the APU 22 has a corresponding DWG coupling circuit 94 on the downstream side of the APU 22. These complementary pairings, upstream / downstream pairings, provide for the coupling of radio carrier signals from an upstream DWG 30 into a corresponding downstream DWG 30 - that is, the next hop transfer. In this figure, the transmission circuit 99 provides this coupling between DWG coupling circuit 94-1 and DWG coupling circuit 94-2.

[0081] For a relay operation of an outbound radio signal, and assuming SIDE 1 is the upstream side of the APU 22 and SIDE 2 is the downstream side, an outbound radio carrier signal appears at DWG 30-1, and the switch 120 of DWG coupling circuit 94-1 (the upstream coupler) is set for reception, such that the outbound radio carrier signal radiates from the upstream DWG 30-1 and couples to the input of the LNA 122 of the upstream coupler. The LNA 122 of the upstream coupler outputs an amplified outbound radio carrier signal and applies it to the input of the S / C 126 of the transmission circuit 99. Next, the S / C 126 applies the outbound radio carrier signal to the input of the PA 124 of DWG coupling circuit 94-2 (the downstream coupler). The PA 124 outputs a power-amplified outbound radio carrier signal, and the switch 120 of the downstream coupler is set for transmission, which means that the outbound radio carrier signal is transmitted into the downstream DWG 30-2 via the antenna 98 of the downstream coupler.

[0082] For a relay operation of an inbound radio signal, and assuming SIDE 1 is the upstream side of the APU 22 and SIDE 2 is the downstream side, an inbound radio carrier signal appears at DWG 30-2, and the switch 120 of the downstream coupler is set for reception, such that the inbound radio carrier signal radiates from the downstream DWG 30-2 and couples to the input of the LNA 122 of the downstream coupler. The LNA 122 of the downstream coupler outputs an amplified inbound radio carrier signal and applies it to the input of the S / C 128 of the transmission circuit 99. Next, the S / C 128 applies the outbound radio carrier signal to the input of the PA 124 of the upstream coupler. The PA 124 of the upstream coupler outputs a power-amplified inbound radio carrier signal, and the switch 120 of the upstream coupler is set for transmission, which means that the inbound radio carrier signal is transmitted into the upstream DWG 30-1 via the antenna 98 of the upstream coupler.

[0083] For base station operation with respect to outbound radio carrier signals received at the APU 22 via the upstream coupler, the S / C 126 of the transmission circuit 99 applies the outbound radio carrier signals to the SW 130 in the S / C 112 that couples it to the antenna circuit 40. The S / C 112 and the S / C 110 split / distribute the outbound radio signals to the respective per-antenna block 96. In embodiments where the APU 22 performs transmit beamforming, the split radio carrier signals to each antenna block 96 are weighted by the beamforming circuit element 108, and the switches 106 and 100 are set for transmission, meaning that the split and weighted radio carrier signals pass to the input of the PA 102 for power amplification and OTA transmission from the associated antenna element.

[0084] For base station operation with respect to OTA radio carrier signals received at the APU 22 via its antenna array 24, the switches 100 and 106 of each antenna block 96 are set for reception, meaning that the antenna received radio carrier signals appear at the input of the LNA 104 in each antenna block 96, which provides low noise amplification of the antenna received radio carrier signals and applies them to the beamforming circuit element 108. In embodiments of the APU 22 that perform receive beamforming, the beamforming circuit element 108 applies weighting to the radio carrier signals output from the LNA 104 and provides them to a respective one of the S / C 110, which combines the radio carrier signals coming in from each antenna block 96. Correspondingly, the S / C 112 forms a combined radio carrier signal, e.g., a combination of the weighted radio carrier signals output from the respective beamforming circuit element 108 of the antenna block 96, and couples the combined radio carrier signal to the switch 130, which is set for inbound base station operation, and thus to the S / C 128.

[0085] Next, the S / C 128 couples the combined radio carrier signal to the PA 124 of the upstream coupler, which provides power amplification thereof and applies it to the switch 120 of the upstream coupler. The switch 120 is configured for transmission, meaning that the combined radio carrier signal from the PA 124 of the upstream coupler is launched as an inbound radio carrier signal into the upstream DWG 30-1 for propagation in the chain 26 toward the CPU 20.

[0086] It will be appreciated that the selective operation of the SW 100, 106, 120, and 130, and the other modal control elements of the first and second radio frequency circuits 90 and 92 of the APU 22, is controlled within the APU 22 by the control circuit 44 of the APU 22, depending on the operating state of the APU 22. In turn, the control circuit 44 of the APU 22 controls the operating state of the APU 22 depending on the control signaling for it by the CPU 20. In this regard, the various SW and S / C within the radio frequency circuits 90 and 92 can be considered as part of the control circuit 44.

[0087] Similarly, the beamforming solution used by the APU 22 for transmitting and / or receiving antenna beamforming - i.e., the dynamically configured set of antenna weights collectively applied by the beamforming circuit elements 108 of the antenna block 96 - can be determined by the CPU 20 and communicated to the APU 22 via control signaling. Thus, the control circuit 44 of the APU 22 includes or interfaces with the beamforming circuit elements 108 to set each antenna weight applied to the radio carrier signals incoming from or outgoing to the antenna array 24.

[0088] As Figure 5 seen in the foregoing, the same or similar RF circuit building blocks are used to implement the antenna circuit 40 and the DWG interface 42. Notably, the elimination of frequency translation blocks and hybrid mode circuitry from the radio carrier signal paths within the APU 22 relaxes the requirements on the integrated circuit process selection that can be used to implement these portions of the APU 22. As other advantages, the absence of filters within the radio carrier signal paths of the APU 22 enables the circuit elements comprising the antenna circuit 40 and the DWG interface 42 to be fully monolithically integrated.

[0089] Before turning to Figure 6 the foregoing, recall that "cell-free massive MIMO" refers to a massive MIMO system in which the BS antennas are geographically dispersed such that each UE 12 can be served by more than one APU 22 and does not experience "cell boundaries" in the traditional sense. The CPU 20 and one or more APUs 22 form a chain 26, in which the chain is interconnected via a fronthaul network comprising respective DWG links 28, and provides a serial hop from the CPU 20 to a first APU 22 in the chain 26 and to each next APU 22 in the chain 26. This scheme provides for a relatively dense deployment of APUs 22 via multiple chains 26, and UEs 12 enjoy corresponding radio link improvements because each UE 12 is typically in close proximity to at least one APU 22.

[0090] Moreover, as noted, each UE 12 can be in proximity to two or more APUs 22, thereby providing increased connection reliability between the UE 12 and the network 10. Figure 6 A possible "system" arrangement is shown, in which three CPUs 20 each anchor two respective chains 26 of APUs 22, with the CPU "1" in the figure anchoring a first and a second chain, while the CPU "2" anchors a third and a fourth chain, and the CPU "3" anchors a fifth and a sixth chain. These chains can be arranged or deployed within and around an overall coverage area of interest, in accordance with an envisaged deployment strategy, which provides for the likelihood that a given UE 12 within the overall coverage area will be relatively close to two or more APUs 22.

[0091] In the envisaged radio communication system 140, which can be used as part of the network 10, a "cloud" 142 comprises computing / control resources 144 for interacting with the CPUs 20, and can represent virtualized processing resources that constitute Figure 1 The RAN 16 and / or CN 18 of the network 10 introduced in the foregoing. For example, the cloud 142 comprises links LI, L2, L3 to the respective CPUs 1, 2, and 3 in the figure, for control plane signaling and / or user plane signaling related to the UEs 12 being served by the CPUs 1, 2, and 3.

[0092] However, while the system description seen in the foregoing provides for the aforementioned non-cellular connection reliability advantages, any serial chain 26 of CPUs 20 and one or more APUs 22 is still susceptible to certain failure events. For example, a failure of the CPU 1 would render the first and second chains inoperative, a failure of the CPU 2 would render the third and fourth chains inoperative, and a failure of the CPU 3 would render the fifth and sixth chains inoperative. Figure 6 Moreover, APU failures that "break" the communication serial link represented by a given chain 26 are contemplated. For example, assume that an intermediate APU 22 in the second chain fails in a manner that breaks the communication link of the radio carrier signal and / or control signaling, which means that the CPU 1 can no longer "reach" the terminal APU 22 (the rightmost APU 22 in the second chain). Note that in the case where the DWG link 28 between APUs 22 comprises more than one DWG, such a failure can affect one or both polarizations or one or more individual DWGs. Also, similarly, a failure in the DWG link 28 or related control signaling interconnection can render APUs 22 downstream of the failure unreachable in the sense of the radio carrier signal and / or uncontrollable in the sense of the control signaling.

[0093]

[0094] ​A CPU failure can thus affect the entire coverage or a large part of the service area, and an APU and / or serial link failure affects all APUs 22 downstream of the failure, which can likewise involve the entire coverage or a large part of the service area.

[0095] Figure 7 A modified version of the arrangement introduced in Figure 6 includes additional elements for improving robustness via failure handling. In particular, Figure 7 The "system" depicted in Figure 6 differs from the system seen in

[0096] The first failover DWG link operates to couple the terminal APU in the second chain with the terminal APU in the third chain, while the second failover DWG link operates to couple the terminal APU in the fourth chain with the terminal APU in the fifth chain. Furthermore, the first failover CPU is coupled to the terminal APU in the first chain, while the second failover CPU is coupled to the terminal APU in the sixth chain. By virtue of this arrangement, each APU in the entire chain or "super chain" formed by the first chain to the sixth chain interconnected in series means that each APU can be connected to any one of the two CPUs. Next, this fact means that if a CPU, APU or DWG link in the super chain fails, the super chain can still continue to provide full coverage for the corresponding service area, albeit it can operate with reduced system capacity in the sense that more UEs 12 can share the same CPU / APU / DWG link resources.

[0097] Further in Figure 7 the cloud 142 comprises a supervision or supervising device 146 comprising processing circuitry 148 and communication interface circuitry 150. These elements of the supervision device 146 are configured to monitor the status of the individual chains 26 (e.g. first chain to sixth chain) e.g. via links LI, L2, L3, L4 and L5. Upon a failure, the "master" CPU of the affected APU is automatically replaced and an alarm is triggered. Here, the "master" CPU refers to the CPU currently controlling the APUs of a given series. In one operational example, in normal operation, CPU 1 is the master CPU for the APUs in the first chain and for the APUs in the second chain. And CPU 2 is the master CPU for the APUs in the third chain and fourth chain.

[0098] Upon detection of a failure of CPU 1, supervisory device 146 activates the first failover CPU (CPU 4 in the figure) as the new master CPU for the first chain of the APU, activates the first failover DWG link, and reconfigures CPU 2 so that it functions as the master CPU for the combined chain comprising the second and third chains. Notably, these master CPU reassignments "reverse" the sense of direction of the affected chains, so that the old upstream direction becomes the new downstream direction, and the old downstream direction becomes the new upstream direction. Accordingly, the advantageous arrangement of the second radio frequency circuitry 92 comprising the DWG interface 42 of each APU 22 seamlessly allows for these changes in sense of direction, since the DWG interface 42 is operable to transmit radio carrier signals from its SIDE-1 DWG link 28 to its SIDE-2 DWG link 28, and vice versa, via simple control of several radio frequency SWs and S / Cs.

[0099] Thus, in normal operation, Figure 7 the system of FIG. 1 can function like Figure 6 the system of FIG. 2, in which the failover elements are inactive. The supervisory device 146, which can be replicated in one or more copies for increased reliability, periodically pings or communicates with the CPUs and APUs in each chain. Upon detection of a failure, the supervisory device 146 triggers an alarm and performs appropriate reconfiguration to repair the failure.

[0100] For example, assume that the first APU in the third chain serves UE 4, and assume that the third APU in the third chain serves UE 3. If the first APU in the third chain fails, then CPU 2 is unable to reach and / or properly control the second and third APUs in that chain. Accordingly, both UE 3 and UE 4 lose their service connections. To remedy this situation, the supervisory device 146 activates the first failover DWG link, and changes the second and third APUs in the third chain to operate using CPU 1 as their new master CPU. The second failover DWG link provides similar flexibility. And, in general, either of the corresponding failover CPUs (CPUs 4 and 5 in the figure) can operate as the master CPU for the entire super chain, if needed. However, again, as more UEs 12 are supported by a CPU, the system can operate at reduced throughput with respect to any particular one of the UEs 12 sharing system resources on a time-division basis.

[0101] Figure 8An example embodiment of a UE 12 is shown, which includes processing circuitry and communication interface circuitry (not shown in the figure). The processing circuitry can be fixed or programmed circuitry or some combination thereof, e.g., one or more digital processors configured according to the execution of computer program instructions. The communication interface circuitry includes, e.g., radio frequency circuitry configured to receive downlink signals via the air interface of the network 10 and to transmit uplink signals via the air interface. The processing circuitry thus operates to control or coordinate the communication interface structure to transmit and receive radio frequency carrier signals according to the radio signal structure (timing, frames, time slots, etc.) used by the network 10.

[0102] Further, the example UE 12 includes four physical "sides", of which two of the sides are shown in the provided perspective view. Each side of the UE 12 includes an antenna array 150, also referred to as a "panel". Based on using each panel to transmit / receive to different APUs, a given UE 12 can enable two panels and benefit from double peak bit rate. The APUs that are "facing" each side of the UE 12 in a directional sense can always acquire data from different chain directions. However, this arrangement can require a change of the master CPU in some APUs in which the change of the master CPU can be triggered in response to the UE 12 requesting very high peak rates.

[0103] In more detail, consider the UE 3 in Figure 7 In a "normal" operating scenario, the UE 3 and the UE 4 are served by the third chain and, thus, time-share the capacity of this chain, e.g., the UE 3 is served at some time and the UE 4 is served at some other time, the respective times being mutually exclusive. Here, it is assumed that the physical location of the UE 3 and the UE 4 is such that the UE 3 can be served by the second APU in the third chain or the last APU in the third chain.

[0104] In case the UE 3 requires a higher bit rate than can be supported via the time-sharing that occurs on the third chain, the supervising device 146 can activate the first failover DWG link and reconfigure the last (terminal) APU in the third chain to use the CPU 1 as its new master CPU. This allows the bandwidth / capacity of the CPU 1 and the associated DWG link 28 of the extended second chain to serve the UE 3, while the UE 3 can also be served by the third chain, with the time-sharing arrangement with the UE 4.

[0105] When replacing the host CPU of a series APU set, the number of APU's in series is typically increased, which degrades the signal-to-noise-and-distortion ratio (SNDR). Assuming each APU adds an equal amount of noise and distortion, the signal quality degrades by 10*log10(#APU). That is, if the number of APU's is doubled, the SNDR is degraded by 3dB due to the interface. This is considered an acceptable degradation, resulting in a reduced peak rate data coverage.

[0106] Figure 3 The control circuit 44 depicted with respect to the example APU 22 supports this flexibility by controlling the state of the APU 22 and managing the direction sense of the APU 22 to allow the host CPU to re-allocate. In one or more embodiments, each APU 22 can be in one of a standby mode, a repeater mode, or a transceiver mode. An APU 22 downstream of an APU 22 operating in the transceiver mode can be in the standby mode. An APU 22 upstream of a transceiving APU 22 operates in the repeater (relay) mode for coupling the active APU 22 to the CPU 20.

[0107] The control circuit 44 listens for control messages from both the upstream direction and the downstream direction. The upstream direction faces the current host CPU 20 of the APU 22, and the control circuit 44 responds to incoming control messages from the current host CPU 20. The downstream direction faces the end of the chain 26 including the APU 22, and the control circuit 44 listens for incoming commands in that direction, signaling a change in the host CPU 20. And, of course, the control circuit 44 is operable to receive control messages from the host CPU 20 and forward / relay them to the next APU 22 in the chain 26.

[0108] Control messages can be forwarded along either chain direction or not at all. In an example embodiment, at startup, all APU's 22 in the chain 26 are in the standby state and are set to not forward control messages. The CPU 20 operating as the host CPU first activates the most recent APU 22 in the chain 26 it is anchored to, selects itself as the host CPU, and instructs the APU 22 to forward control messages. The next APU 22 in each chain 26 anchored by the CPU 20 is then activated, and this continues until all APU's 22 belonging to each CPU 20 are activated. The last APU 22 in series (i.e., the chain termination APU 22) is instructed not to perform the next hop forwarding.

[0109] Thus, if the master CPU 20 requires a change for the chain 26, the APU 22 in the chain 26 furthest downstream from the old master CPU 20 receives from the new master CPU 20 and requests the APU 22 to forward control signaling from the new master CPU 20 in the old upstream direction of the chain 26 to sequentially reconfigure each remaining APU 22 in the chain 26 to change their master CPU affiliation. When not transmitting control signaling, the control signaling interface 48 of the control circuit 44 can be placed in a high-ohmic state to prevent contention with the APUs 22 and / or CPUs 20 at the other end of its serial control signaling link.

[0110] Figure 9 An example method 900 of operating an APU 22, also referred to herein as a radio communication node (RCN) 22, is shown. The method 900 envisions positioning the radio communication node 22 as one in a serial link of radio communication nodes 22. Here, the serial link can be viewed as a chain 26 formed using interconnecting dielectric waveguides as DWG links 28 representing a serial link or hop that serially interconnects the radio communication node 22 to a central processing unit 20 that anchors the chain 26 and that transmits radio carrier signals out via the serial link for over-the-air transmission by a particular one of the radio communication nodes 22 and that receives inbound radio carrier signals via the serial link for processing by the central processing unit 20. The central processing unit 20 can also be referred to as a CPU or central processing node or CPN.

[0111] The method 900 includes, in the case that an outbound radio carrier signal is targeted for a user equipment 12 served by the radio communication node 22 (the “BS” path from block 904), receiving (block 902) the outbound radio carrier signal traveling in an outbound direction along the serial link and performing (block 906) over-the-air transmission of the outbound radio carrier signal, and, in the case that the outbound radio carrier signal is not targeted for a user equipment (12) served by the radio communication node 22 (the “relay” path from block 904), propagating (block 908) the outbound radio carrier signal along a next outbound hop of the serial link.

[0112] The method 900 also includes, possibly at different times or at different time intervals, receiving (block 910) an inbound radio carrier signal traveling in an inbound direction along the serial link and propagating (block 912) the inbound radio carrier signal along a next inbound hop of the serial link.

[0113] Alternatively, at another time interval or at another moment, method 900 includes: APU 22 receiving (box 914) a radio carrier signal transmitted over the air from user equipment 12 served by radio communication node 22, and propagating (box 916) the received radio carrier signal as an inbound radio carrier signal along the next inbound hop of the serial link.

[0114] Figure 10 Another embodiment of APU 22 is shown, which can be at least partially implemented as a collection 1000 of functional processing "units" or "modules" via a programming configuration of computer processing circuitry (e.g., one or more microcontrollers). APU 22 includes a control module 1002 configured to receive control messages from the main CPU directly or from the next adjacent APU 22 in a chain 26 including APU 22.

[0115] Control module 1002 responds to control signaling to control the operation of APU 22 and can pass some or all of the control signaling downstream to the next adjacent APU 22 in chain 26. For example, regarding Figure 5 Depending on whether the APU 22 is operating in standby state or mode, base station (transceiver) state or mode, or repeater (relay) state or mode, the control module 1002 provides discrete control signals to control various switches and the state or operation of the splitter / combiner, including the antenna circuit 40 of the APU 22 and the DWG interface 42. The assembly 1000 also includes a timing module 1004, which is configured to maintain the timing of the APU 22, for example, timing related to or dependent on timing information transmitted in the control signaling.

[0116] Figure 11 An embodiment of the DWG interface 42 envisioned for APU 22 is shown, and early details regarding support for multi-polarization are elaborated. The DWG link 28-1 on SIDE 1 of the APU 22 involved includes a first DWG and a second DWG, wherein each DWG corresponds to a different radio carrier signal polarization. That is, each APU 22 can support transmission and / or reception using two different polarizations.

[0117] Similarly, the DWG link 28-2 on the SIDE 2 of the APU 22 involved includes a first DWG and a second DWG, where each DWG corresponds to one of the different radio carrier signal polarizations. Specifically, the first DWG of the DWG link 28-1 pairs or corresponds with the first DWG of the DWG link 28-2, meaning that they are complementary upstream / downstream DWG pairs for handling upstream / downstream transfer of radio carrier signals associated with a first polarization. The second DWG of the DWG link 28-1 pairs or corresponds with the second DWG of the DWG link 28-2, meaning that they are complementary upstream / downstream DWG pairs for handling upstream / downstream transfer of radio carrier signals associated with a second polarization.

[0118] It should be noted that modifications and other embodiments of the disclosed application are contemplated; as would be apparent to one skilled in the art having the benefit of the teachings of the present description and associated drawings. Therefore, it is to be understood that the application is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the disclosure. Although specific terms can be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A radio communication system (140) comprising: a central processing unit (20) and two or more radio communication nodes (22) connected in series as a chain (26), each serial link in the chain (26) comprising a dielectric waveguide link (28) and each serial link having a downstream direction away from the central processing unit (20) and an upstream direction towards the central processing unit (20); wherein the central processing unit (20) is configured to control individual ones of the radio communication nodes (22) to operate as a base station or a relay station; wherein any given radio communication node (22) operating as a base station: receives an outbound radio carrier signal generated by the central processing unit (20) and propagated along the downstream direction via the chain (26) and transmits the outbound radio carrier signal over the air as a downlink radio carrier signal for reception by one or more user equipment (12) served by the base station; or receives radio carrier signals over the air as uplink radio carrier signals originating from one of the user equipment (12) served by the base station and propagates the received radio carrier signals along the upstream direction via the chain (26) for processing by the central processing unit (20); and wherein any given radio communication node (22) operating as a relay station: receives inbound radio carrier signals propagated along the upstream direction in the chain (26) and propagates them to the next upstream hop in the chain (26); or receives outbound radio carrier signals propagated along the downstream direction in the chain (26) and propagates them to the next downstream hop in the chain (26), and wherein only the central processing unit (20) provides: modulation and frequency conversion, demodulation and frequency conversion, or modulation, demodulation and frequency conversion.

2. A radio communication node (22) comprising an antenna circuit (40) and a dielectric waveguide interface (42), wherein, In a relay operation, the dielectric waveguide interface (42) is configured to relay radio carrier signals between a first dielectric waveguide link (28-1) and a second dielectric waveguide link (28-2), and in a base station operation, the dielectric waveguide interface (42) is configured to couple radio carrier signals incoming via the first dielectric waveguide link (28-1) into the antenna circuitry (40) for over-the-air transmission and to couple radio carrier signals incoming via the antenna circuitry (40) into the first dielectric waveguide link (28-1) for waveguide transport towards a central processing unit (20), wherein the central processing unit (20) provides modulation and frequency conversion, demodulation and frequency conversion, or modulation, demodulation and frequency conversion for all radio carrier signals processed by the radio communication node (22), wherein only the central processing unit (20) provides: modulation and frequency conversion, demodulation and frequency conversion, or modulation, demodulation and frequency conversion.

3. The radio communication node (22) of claim 2, wherein, The antenna circuit (40) is configured for over-the-air transmission of radio carrier signals via an antenna array (24) and for over-the-air reception of radio carrier signals via the antenna array (24); and The dielectric waveguide interface (42) is coupled to the antenna circuit (40) and configured for series interconnection of the radio communication node (22), the dielectric waveguide interface (42) comprising a first coupling circuit (94-1) for transmitting radio carrier signals into a first dielectric waveguide (30-1) and receiving radio carrier signals from the first dielectric waveguide (30-1), and further comprising a second coupling circuit (94-2) for transmitting radio carrier signals into a second dielectric waveguide (30-2) and receiving radio carrier signals from the second dielectric waveguide (30-2); and wherein the radio communication node (22) further comprises a control circuit (44) that configures the radio communication node (22) for a relay operation or a base station operation, and wherein: In the base station operation, the antenna circuit (40) receives received radio carrier signals via over-the-air are coupled into the dielectric waveguide interface (42) and transmitted into at least one of the first dielectric waveguide (30-1) and the second dielectric waveguide (30-2), and radio carrier signals received by the dielectric waveguide interface (42) are coupled into the antenna circuit (40) for over-the-air transmission; and In the relay operation, radio carrier signals received from the first dielectric waveguide (30-1) via the first coupling circuit (94-1) are coupled into the second coupling circuit (94-2) and transmitted into the second dielectric waveguide (30-2), and radio carrier signals received from the second dielectric waveguide (30-2) via the second coupling circuit (94-2) are coupled into the first coupling circuit (94-1) and transmitted into the first dielectric waveguide (30-1).

4. The radio communication node (22) according to claim 3, wherein The control signaling indicates timing of a time division duplex, TDD, operation of the radio communication node (22) such that, in the base station operation, the radio communication node (22) receives or transmits via the antenna circuit (40) and associated antenna array (24), and such that, in the relay operation, the radio communication node (22) relays radio signals towards or away from the central processing unit (20). The control signaling indicates timing of a time division duplex, TDD, operation of the radio communication node (22) such that, in the base station operation, the radio communication node (22) receives or transmits via the antenna circuit (40) and associated antenna array (24), and such that, in the relay operation, the radio communication node (22) relays radio signals towards or away from the central processing unit (20).

5. The radio communication node (22) according to claim 3 or 4, wherein, The central processing unit (20) is a first central processing unit (20-1) associated with a first end of a serial link, and wherein a second central processing unit (20-2) is associated with another end of the serial link, and wherein, in response to an indication of a change of control from the first central processing unit (20-1) to the second central processing unit (20-2) in response to incoming supervisory signaling of the radio communication node (22), the control circuit (44) is configured to reconfigure the radio communication node (22) to exchange upstream coupling roles and downstream coupling roles played by the first coupling circuit (94-1) and the second coupling circuit (94-2).

6. The radio communication node (22) according to claim 3 or 4, wherein, The first coupling circuit (94-1) comprises a first set of coupling circuits, while the second coupling circuit (94-2) comprises a second set of coupling circuits, and wherein each coupling circuit of the first set maps to a respective coupling circuit of the second set as an upstream / downstream coupler pair, and each upstream / downstream coupler pair handles a different polarization of radio carrier signals.

7. The radio communication node (22) according to claim 6, wherein For each polarization of radio carrier signals handled by the radio communication node (22), there are two or more upstream / downstream coupler pairs, enabling the radio communication node (22) to simultaneously relay and / or transceive two or more radio carrier signals.

8. The radio communication node (22) of claim 2, wherein The dielectric waveguide interface (42) comprises a second radio frequency circuit (92) configured to pass radio carrier signals received via one of two respective coupling circuits (94) of the dielectric waveguide interface (42) to the other one of the two respective coupling circuits (94) or to an antenna circuit (40) of the radio communication node (22), wherein each coupling circuit (94) is configured for transmitting and receiving radio carrier signals to and from a respective dielectric waveguide (30) included in a dielectric waveguide DWG link (28) or hop, and for coupling the radio communication node (22) to another radio communication node (22) or a central processing unit (20) providing processing for all radio carrier signals handled by the radio communication node (22); wherein the antenna circuit (40) comprises a first radio frequency circuit (90) configured to transmit radio carrier signals passed to the antenna circuit (40) from the dielectric waveguide interface (42) via the associated antenna array (24), and to pass radio carrier signals received via the antenna array (24) to the dielectric waveguide interface (42); and The radio communication node (22) further comprises a control circuit (44) comprising a signaling interface circuit (48) for exchanging control signaling directly or indirectly with the central processing unit (20) and configured to control the dielectric waveguide interface (42) and the antenna circuit (40) in response to the control signaling.

9. The radio communication node (22) according to claim 8, wherein, The radio communication node (22) is configured for time division duplex, TDD, operation, wherein transmission and reception of radio carrier signals is mutually exclusive for the antenna circuit (40) and for each coupling circuit (94) of the dielectric waveguide interface (42).

10. The radio communication node (22) according to claim 9, wherein, The control circuit (44) is configured to control TDD operation of the antenna circuit (40) and the dielectric waveguide interface (42).

11. The radio communication node (22) according to any of claims 8 to 10, wherein, The antenna circuit (40) is configured for at least one of receive beamforming via the antenna array (24) and transmit beamforming via the antenna array (24), wherein the control signaling comprises beamforming control signaling, and wherein the control circuit (44) controls receive beamforming or transmit beamforming of analog beamforming circuit elements (108) in the antenna circuit (40) in accordance with the beamforming control signaling.

12. The radio communication node (22) according to any of claims 8 to 10, wherein, The signaling interface circuit (48) is configured to electrically couple with a conductive exterior (52) used on a respective dielectric waveguide (30) comprising the DWG link (28) coupled to the radio communication node (22).

13. The radio communication node (22) of claim 2, wherein, The antenna circuit (40) is configured for over-the-air transmission of radio carrier signals via an antenna array (24) and for over-the-air reception of radio carrier signals via the antenna array (24); and wherein the dielectric waveguide interface (42) is coupled to the antenna circuit (40) and configured for a serial link of the radio communication node (22) with a central processing unit (20) controlling the radio communication node (22) in series, the dielectric waveguide interface (42) comprising a first coupling circuit (94-1) for transmitting radio carrier signals into a first dielectric waveguide (30-1) and receiving radio carrier signals from the first dielectric waveguide (30-1), and further comprising a second coupling circuit (94-2) for transmitting radio carrier signals into a second dielectric waveguide (30-2) and receiving radio carrier signals from the second dielectric waveguide (30-2); wherein coupling circuits in the first coupling circuit (94-1) and the second coupling circuit (94-2) facing the central processing unit (20) in the series link act as upstream couplers, while coupling circuits facing away from the central processing unit (20) in the series link act as downstream couplers; and wherein the radio communication node (22) further comprises a control circuit (44) that configures the radio communication node (22) for a relay operation or a base station operation in response to control signaling originating from the central processing unit (20), and wherein: in the base station operation, the antenna circuit (40) receives received radio carrier signals via air into the dielectric waveguide interface (42) and transmits via the upstream coupler towards the central processing unit (20) for processing, and the dielectric waveguide interface (42) receives radio carrier signals via the upstream coupler into the antenna circuit (40) for air transmission; and in the relay operation, radio carrier signals received via the upstream coupler are coupled to the downstream coupler and transmitted towards the next radio communication node (22) in the serial interconnection, while radio carrier signals received via the downstream coupler are coupled to the upstream coupler and transmitted by the upstream coupler towards the central processing unit (20).

14. A method (900) of operating a radio communication node (22) that is positioned as one of a serial link of radio communication nodes (22), the serial link comprising an interconnecting dielectric waveguide (30) referred to as a dielectric waveguide, DWG, link (28) or hop and serially interconnecting the radio communication nodes (22) to a central processing unit (20) that anchors the serial link and transmits outbound radio carrier signals via the serial link for air transmission by radio communication nodes in an outbound direction and receives inbound radio carrier signals via the serial link for processing by the central processing unit (20), and the method (900) comprising: receiving (902) outbound radio carrier signals traveling along the serial link in an outbound direction in case the outbound radio carrier signals target user equipment (12) served by the radio communication node (22) and performing (906) air transmission of the outbound radio carrier signals, while propagating (908) the outbound radio carrier signals along a next outbound hop of the serial link in case the outbound radio carrier signals do not target user equipment (12) served by the radio communication node (22); receiving (910) inbound radio carrier signals traveling along the serial link in an inbound direction and propagating (912) the inbound radio carrier signals along a next inbound hop of the serial link; and receiving (914) as air transmitted radio carrier signals from user equipment (12) served by the radio communication node (22) and propagating (916) the received radio carrier signals as inbound radio carrier signals along a next inbound hop of the serial link, wherein only the central processing unit (20) is configured to perform: modulation and frequency conversion, demodulation and frequency conversion, or Modulation, demodulation and frequency conversion.

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