Patent Description:
Wireless communications networks, such as cellular networks, typically comprise a plurality of distributed radio nodes (e.g. base stations) which are connected to a core network. Each radio node provides wireless communications capabilities to end-user nodes within a particular geographic region. In other words, each radio node connects end-user nodes to the core network via wireless communication links. The radio nodes are typically connected to the core network via one or more backhaul links that are established between the radio node and a network device (e.g. a base station controller) that is connected to, or has access to, the core network. The information that is exchanged over the backhaul network is referred to herein as backhaul information.

Backhaul information is ideally exchanged over one or more fibre optic backhaul links to achieve high throughput of backhaul information between the remote radio node and the corresponding network device. However, establishing a fibre optic backhaul link is not always feasible, or practical, due to, for example, high installation costs. Accordingly, in many cases backhaul information is exchanged over one or more point-to-point radio backhaul links established between a remote radio node and an anchor radio node (a radio node that is connected to or has access to the core network).

Reference is now made to <FIG> which illustrates a first example system <NUM> for exchanging backhaul information over point-to-point radio backhaul links that is known to the Applicant. The statement that a feature (e.g. system <NUM>) is known to the Applicant is not an admission that the feature is well-known. In this example, which may be referred to as a microwave backhauling system, backhaul information is exchanged between a remote radio node <NUM> and an anchor radio node <NUM> over a dedicated point-to-point radio backhaul link <NUM> established using a frequency bandwidth (FBACKHAUL) which is separate and distinct from the frequency bandwidth (FEND-USER) used by the radio nodes <NUM>, <NUM> to provide uplink and downlink radio access connectivity <NUM> to one or more end-user nodes <NUM>. The frequency bandwidth (FBACKHAUL) used to establish the dedicated point-to-point radio backhaul link <NUM> is typically in the microwave frequency range of the electromagnetic spectrum. Due to technology evolution and availability of wide channel bandwidths, the V-band (<NUM>-<NUM>) and the E-Band (<NUM>-<NUM>) have been identified as being suitable for establishing high-throughput dedicated backhaul communication links between remote radio nodes and anchor radio nodes. The W-band (<NUM>-<NUM>) and D-band (<NUM>-<NUM>) have also been identified as being potentially suitable for use in establishing dedicated backhaul communications links between remote radio nodes and anchor radio nodes.

However, radio backhaul links operating over high frequency bandwidths, such as the E-band, W-band or D-band, can generally provide high capacity, but they are limited in terms of reach and coverage due to poor link budget and severe rain fading that can affect the propagation over high frequency bandwidths. Furthermore, the light licensing paradigm and the lack of a harmonized regulation characterizing some frequency bands, such as the V-band, inherently lead to over-conservative link planning designs to counteract the additional interference that may be produced by other co-channel systems. These factors make the throughput availabilities typically required to implement microwave backhaul links very challenging, particularly in light of the inter-site distance (e.g. <NUM>-<NUM> for urban environments and <NUM>-<NUM> for rural environments) expected in future wireless networks.

Reference is now made to <FIG> which illustrates a second example system <NUM> for exchanging backhaul information over point-to-point radio backhaul links that is known to the Applicant. In this example, which may be referred to as a dual-band backhauling system, backhaul information is exchanged between a remote radio node <NUM> and an anchor radio node <NUM> over at least two dedicated point-to-point radio backhaul links <NUM>, <NUM> established using two disjoint frequency bands (FBACKHAUL, FBACKHAUL2) that are separate and distinct from the frequency bandwidth (FEND-USER) used by the radio nodes <NUM>, <NUM> to provide uplink and downlink radio access connectivity <NUM> to the end-user nodes <NUM>. The two frequency bandwidths (FBACKHAUL, FBACKHAUL2) used to establish the radio backhaul links <NUM>, <NUM> are typically characterized by different propagation and regulatory conditions. Dual-band backhauling systems generally increase the reliability of backhaul throughput over systems, such as system <NUM> of <FIG>, which use a single frequency bandwidth to establish the backhaul link(s), by exploiting the diverse channel conditions over the two disjoint frequency bands. However, such dual-band backhauling systems <NUM> are generally more complex than systems, such as system <NUM> of <FIG>, which use a single frequency bandwidth to establish the radio backhaul link(s), since the radio nodes require additional hardware and logic to be able to support communications over multiple frequency bandwidths.

<CIT> discloses apparatus for wireless communication. A first base station may provide first backhaul information using a shared channel to a second base station. The shared channel may be white space channels, Authorized Shared Multiuser (ASM) channels or an Instrumentation, Scientific, and Measurement (ISM) channels. The first base station may further provide second backhaul information using a legacy backhaul channel.

<CIT> discloses systems and methodologies that facilitate providing opportunistic relay node communication based on scheduling of other communications in a wireless network. A relay node can maintain a backhaul link with an access point and an access link with a mobile device to facilitate communicating information therebetween. Time slots during which the backhaul link is active can be determined and avoided during scheduling access link communications with the mobile device.

<CIT> discloses methods and apparatus for aggregating carriers over a backhaul link between a relay and an eNB. A first set of subframes of at least a first carrier of a plurality of carriers configured for communicating with an eNB over a backhaul link can be determined. A second set of subframes of at least a second carrier of the plurality of carriers configured for backhaul link communications is also determined, wherein the second set of subframes are different from the first set of subframes. Data received over a plurality of access link carriers can then be communicated to the eNB over the first carrier and the second carrier based at least on the first set of subframes and the second set of subframes.

The embodiments described below are provided by way of example only and are not limiting of implementations which solve any or all of the disadvantages of radio backhauling architectures and systems known to the Applicant.

It is an object of the invention to have a backhaul architecture which enables high capacity backhaul links with higher minimum guaranteed throughputs compared to known microwave backhauling systems, such as the system <NUM> of <FIG>.

Further implementation forms are apparent from the dependent claims, the detailed description and the figures.

According to the invention, a first aspect provides a control unit for controlling a radio node comprising a first radio unit and a second radio unit, the control unit configured to: generate and output one or more control signals to cause: the first radio unit to exchange a first portion of backhaul information with another radio node over a first communication link established using a first frequency bandwidth; the second radio unit to provide uplink and downlink radio access connectivity to one or more end-user nodes using a second frequency bandwidth, wherein the second frequency bandwidth being different from the first frequency bandwidth; and the second radio unit to exchange a second portion of the backhaul information with the other radio node over a second communication link established using the second frequency bandwidth.

The control unit may be configured to dynamically allocate none or a portion of the second frequency bandwidth for use in establishing the second communication link based at least on a determined quality of the first communication link.

According to the invention, the control unit is configured to allocate none of the second frequency bandwidth for use in establishing the second communication link in response to determining that a quality of the first communication link is greater than or equal to a minimum quality, and allocate a portion of the second frequency bandwidth for use in establishing the second communication link in response to determining that the quality of the first communication link is less than the minimum quality.

The control unit may be configured to determine that the quality of the first communication link is less than the minimum quality in response to determining that a throughput of backhaul information transmitted from the first radio unit over the first communication link is less than a first threshold, and/or that a throughput of backhaul information received by the first radio unit over the first communication link is less than a second threshold.

The control unit may be configured to allocate none or a portion of the second frequency bandwidth for establishing the second communication link by time partitioning a radio access frame into a plurality of epochs and outputting one or more control signals to cause the second radio unit to perform, in each of the plurality of epochs, one or more of: provide uplink radio access connectivity to one or more end-user nodes using the second frequency bandwidth, provide downlink radio access connectivity to one or more end-user nodes using the second frequency bandwidth, transmit backhaul information to the other radio node using the second frequency bandwidth, and receive backhaul information from the other radio node using the second frequency bandwidth based on at least a quality of the first communication link.

The control unit may be configured to, in response to determining that the quality of the first communication link is greater than or equal to the minimum quality, divide a radio access frame into two epochs and output one or more control signals to cause the second radio unit to: only provide downlink radio access connectivity to the one or more end-user nodes in one epoch of the two epochs; and only provide uplink radio access connectivity to the one or more end-user nodes in the other epoch of the two epochs.

The control unit may be configured to, in response to determining that the quality of the first communication link is less than the minimum quality and that the second radio unit does not support spatial multiplexing, divide a radio access frame into four epochs and output one or more control signals to cause the second radio unit to: provide downlink radio access connectivity to the one or more end-user nodes using the second frequency bandwidth in one epoch of the four epochs; provide uplink radio access connectivity to the one or more end-user nodes using the second frequency bandwidth in another epoch of the four epochs; transmit backhaul information to the other radio node using the second communication link in yet another epoch of the four epochs; and receive backhaul information from the other radio node via the second communication link in the remaining epoch of the four epochs.

The control unit may be configured to, in response to determining that the quality of the first communication link is less than the minimum quality and that the second radio unit supports spatial multiplexing, divide a radio access frame into four epochs and output one or more control signals to cause the second radio unit to: concurrently provide downlink radio access connectivity to one or more end-user nodes and transmit backhaul information to the other radio node using the second frequency bandwidth during one epoch of the four epochs; concurrently provide uplink radio access connectivity to one or more end-user nodes and receive backhaul information from the other radio node using the second frequency bandwidth during another epoch of the four epochs; only provide downlink radio access connectivity to one or more end-user nodes using the second frequency bandwidth during yet another epoch of the four epochs; and only provide uplink radio access connectivity to one or more end-user nodes using the second frequency bandwidth during the remaining epoch of the four epochs.

The second radio unit may be configured to provide uplink and downlink radio access connectivity to a plurality of end-user nodes; and the one or more control signals may be configured to cause the second radio unit to provide downlink radio access connectivity to a first subset of the plurality of end-user nodes during the one epoch and provide downlink radio access connectivity to a different subset of the plurality of end-user nodes in the yet another epoch so as to maximize a function of one or more of an uplink radio access connectivity throughput provided to the plurality of end-user nodes, a downlink radio access connectivity throughput provided to the plurality of end-user nodes, a throughput of the backhaul information transmitted to the other radio node via the second communication link over the second frequency bandwidth, and a throughput of the backhaul information received from the other radio node via the second communication link over the second frequency bandwidth.

The control unit may be configured to, in response to determining that the quality of the first communication link is less than the minimum quality and that the second radio unit supports spatial multiplexing, divide a radio access frame into two epochs and output one or more control signals to cause the second radio unit to: concurrently provide downlink radio access connectivity to one or more end-user nodes and transmit backhaul information to the other radio node using the second frequency bandwidth during one epoch of the two epochs; and concurrently provide uplink radio access connectivity to one or more end-user nodes and receive backhaul information from the other radio node using the second frequency bandwidth during another epoch of the two epochs.

The control unit may be configured to select a duration of the plurality of epochs so as to maximize a function of one or more of an uplink radio access connectivity throughput provided to the one or more end-user nodes, a downlink radio access connectivity throughput provided to the one or more end-user nodes, a throughput of the backhaul information transmitted to the other radio node via the second communication link over the second frequency bandwidth, and a throughput of the backhaul information received from the other radio node via the second communication link over the second frequency bandwidth.

The control unit may be configured to select a duration of each epoch based at least on one or more of: an uplink radio access connectivity throughput provided by the second radio unit to the one or more end-user nodes, a downlink radio access connectivity throughput provided by the second radio unit to the one or more end-user nodes, an uplink radio access connectivity throughput provided by the other radio node to one or more end-user nodes, a downlink radio access connectivity throughput provided by the other radio node to one or more end-user nodes, a throughput of the backhaul information transmitted to the other radio node via the second communication link over the second frequency bandwidth, a throughput of the backhaul information received from the other radio node via the second communication link over the second frequency bandwidth, a throughput of backhaul information transmitted to the other radio node via the first communication link over the first frequency bandwidth, and a throughput of backhaul information received from the other radio node via the first communication link over the first frequency bandwidth.

The control unit may be configured to periodically determine the quality of the first communication link and update the allocation based on the determination.

The control unit may be configured to determine the quality of the first communication link and update the allocation after N radio access frames, wherein N is an integer greater than or equal to one.

The second radio unit may be configured to provide uplink and downlink radio access connectivity to a plurality of end-user nodes; and the one or more control signals may be configured to cause the second radio unit to provide uplink radio access connectivity to a first subset of the plurality of end-user nodes during the another epoch and provide uplink radio access connectivity to a different subset of the plurality of end-user nodes in the remaining epoch so as to maximize a function of one or more of an uplink radio access connectivity throughput provided to the plurality of end-user nodes, a downlink radio access connectivity throughput provided to the plurality of end-user nodes, a throughput of the backhaul information transmitted to the other radio node via the second communication link over the second frequency bandwidth, and a throughput of the backhaul information received from the other radio node via the second communication link over the second frequency bandwidth.

The control unit may be configured to select a duration of each epoch so as to maximize a function of an uplink radio access connectivity throughput provided to the one or more end-user nodes and/or a downlink radio access connectivity throughput provided to the one or more end-user nodes, while guaranteeing a minimum quality to at least one of: uplink radio access connectivity throughput provided to the one or more end-user nodes by the radio node, downlink radio access connectivity throughput provided to the one or more end-user nodes by the radio node, uplink radio access connectivity throughput provided to one or more end-user nodes by the other radio node, and downlink radio access connectivity throughput provided to one or more end-user nodes by the other radio node.

The backhaul information may comprise one or more subsets of backhaul information each associated with a priority, and the control unit may be configured to select one or more subsets to be transmitted over the second communication link based on the priority associated with the one or more subsets and output one or more control signals to cause the selected subsets to be transmitted by the second radio unit over the second communication link.

The control unit may be configured to select a duration of the epochs within an infinite resolution or within a discrete set with a finite number of possibilities.

When the radio node supports spatial multiplexing the one or more control signals generated by the control unit may be adapted for the specific multiplexing mode supported by the radio node.

The other radio node may be configured to provide uplink and downlink radio access connectivity to one or more end-user nodes using the second frequency bandwidth and the control unit may be further configured to generate the first threshold as a function of downlink radio access connectivity spectral efficiencies provided by the other radio node to the one or more end-user nodes using the second frequency bandwidth, and generate the second threshold as a function of uplink radio access connectivity spectral efficiencies provided by the other radio node to the one or more end-user nodes using the second frequency bandwidth.

As example, a second aspect provides a radio node comprising: a first radio unit configured to exchange a first portion of backhaul information with another radio node over a first communication link established using a first frequency bandwidth; and a second radio unit configured to: provide uplink and downlink radio access connectivity to one or more end-user nodes using a second frequency bandwidth, the second frequency bandwidth being different from the first frequency bandwidth; and exchange a second portion of the backhaul information with the other radio node over a second communication link established using the second frequency bandwidth.

The first portion of the backhaul information may be a portion of the backhaul information that can be reliably carried over the first frequency bandwidth, and the second portion of the backhaul information corresponds to the amount of backhaul information that can be reliably carried over the second frequency bandwidth.

The radio node may further comprise an interface unit that is configured to adapt information received via one of the first and second radio units so that it is suitable for transmission by the other of the first and second radio units.

The second radio unit may comprise an antenna unit that comprises a plurality of antenna elements to support multiple-input-multiple-output communications.

A third aspect provides a system comprising the radio node of the second aspect and the control unit of the first aspect, wherein the control unit is configured to control the radio node.

The radio node may be connected to a core network by a fibre link; and the system may further comprise the other radio node, the other radio node not being directly connected to the core network by a fibre link, the other radio node comprising: a third radio unit configured to exchange the first portion of backhaul information with the radio node using the first frequency bandwidth; and a fourth radio unit configured to: provide uplink and downlink radio access connectivity to one or more end-user nodes using the second frequency bandwidth; and exchange the second portion of the backhaul information with the radio node (<NUM>-A) using the second frequency bandwidth.

According to the invention, a fourth aspect provides a method of exchanging backhaul information between a radio node and another radio node, the method comprising: exchanging a first portion of the backhaul information over a first communication link established using a first frequency bandwidth; and exchanging a second portion of the backhaul information over a second communication link established using a second frequency bandwidth, the second frequency bandwidth being different from the first frequency bandwidth and being used by at least one of the radio nodes to provide uplink and downlink radio access connectivity to one or more end-user nodes, the method further comprising allocating none of the second frequency bandwidth for use in establishing the second communication link in response to determining that a quality of the first communication link is greater than or equal to a minimum quality, and allocating a portion of the second frequency bandwidth for use in establishing the second communication link in response to determining that the quality of the first communication link is less than the minimum quality.

According to further implementations of the fourth aspect, the method further comprises steps for carrying out the functionalities of the units described above in connection with the control unit, the radio node and the system of the first to third aspect.

According to the invention, a fifth aspect provides a computer-program product including computer executable instructions that, when executed by a processor perform the steps of the method according to the fifth aspect.

The present invention is described by way of example with reference to the accompanying drawings. In the drawings:.

Embodiments are described by way of example only.

Described herein are methods, systems and control units for controlling radio nodes, wherein radio nodes exchange backhaul information with at least one other radio node jointly over a first communication link established using a first frequency bandwidth (FBACKHAUL); and a second communication link established using a second frequency bandwidth (FEND-USER) that is also used by the radio nodes to provide uplink and downlink radio access connectivity to one or more end-user nodes. Such methods, systems and control units enable high capacity backhaul links with a higher minimum guaranteed throughput compared to known microwave backhauling systems, such as the system <NUM> of <FIG>, which use a single point-to-point dedicated microwave backhaul link. Furthermore, since in the methods, systems and control units described herein the radio nodes only use two frequency bandwidths (FBACKHAUL, FEND-USER) to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information, they are more efficient and less complex compared to systems, such as the system <NUM> of <FIG>, in which the radio nodes use three different frequency bandwidths (FBACKHAUL, FBACKHAUL2, FEND-USER) to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information.

In some cases, the second communication link (i.e. the communication link established using the second frequency bandwidth) may be dynamically established based on the quality of the first communication link (i.e. the communication link established over the first frequency bandwidth). The second communication link establishes when the quality of the first communication link falls below a minimum quality (e.g. when the throughput of backhaul information transmitted from a radio node to another radio node is below a first threshold and/or the throughput of the backhaul information received by the radio node from the other radio node is below a second threshold). When the second communication link is established the portion or amount of the second frequency bandwidth used to establish the second communication link may be dynamically adjusted based at least on the quality of the first communication link. This allows for efficient use of the frequency bandwidths as the second frequency bandwidth can be dedicated to providing uplink and downlink radio access connectivity when the first communication link is above a minimum quality and at least a portion of the second frequency bandwidth can be dynamically allocated for transporting backhaul information to supplement the first communication link when the quality of the first communication link falls below the minimum quality.

This makes the described methods, systems and control units suitable for scenarios where the end-user nodes spatial density and traffic intensity is positively correlated with the quality of the dedicated point-to-point backhaul link established using the first frequency bandwidth, such as outdoor scenarios affected by adverse meteorological conditions. In these cases, a large portion of the second frequency bandwidth can be used for transporting backhaul information to compensate for the capacity loss temporarily experienced over the first communication link during adverse meteorological conditions.

In some cases, either none (when the first communication link does meet a minimum quality threshold) or at least a portion of the second frequency bandwidth (when the first communication link does not meet a minimum quality threshold) allocated for use in establishing the second communication link (e.g. allocated for use in transporting backhaul information) by time partitioning radio access frames for the second frequency bandwidth into a plurality of epochs wherein the radio nodes perform one or more of the following in each epoch based on at least the quality of the first communication link: provide uplink radio access to end-user nodes using the second frequency bandwidth, provide downlink radio access to end-user nodes using the second frequency bandwidth, transmit backhaul information using the second frequency bandwidth, and receive backhaul information using the second frequency bandwidth. The duration of the epochs may be selected so as to find a balance between guaranteed uplink/downlink radio access connectivity throughput and backhaul throughput. The duration of the epochs may be selected or chosen within an infinite resolution interval or within a discrete set with a finite number of possibilities.

The term radio access frame is used herein to mean a time period in which a radio node transmits and/or receives signals over a certain frequency bandwidth. Accordingly, a radio access frame for the second frequency bandwidth is a time period in which a radio node transmits and/or receives signals over the second frequency bandwidth.

Reference is now made to <FIG> which illustrates an example backhauling system <NUM> wherein backhaul information is exchanged between radio nodes jointly over a first communication link established using a first frequency bandwidth (FBACKHAUL); and a second communication link established using a second frequency bandwidth (FEND-USER) that is also used by the radio nodes to provide uplink and downlink radio access connectivity to one or more end-user nodes.

The system <NUM> comprises a first radio node <NUM>-A and a second radio node <NUM>-B. The radio nodes <NUM>-A, <NUM>-B may be any device, such as, but not limited to, a base station or a wireless access point, that is capable of establishing radio communications with end-user nodes and with other radio nodes. The first radio node <NUM>-A is connected to (or has access to) a core network <NUM> and as a result may be referred to as an anchor radio node. The first radio node <NUM>-A may be connected to the core network <NUM> in any suitable manner, such as, but not limited to, via an optical fibre point of presence. The second radio node <NUM>-B does not have a wired connection to the core network <NUM> and as a result may be referred to as a remote radio node. Since the second radio node <NUM>-B is not connected to the core network <NUM> the second radio node exchanges backhaul information with the first radio node <NUM>-A. The term "backhaul information" is used herein to mean information that is transmitted to/from the remote radio node from/to the core network and may include: communications to/from the anchor radio node (e.g. the first radio node <NUM>-A) from/to the remote radio node (e.g. the second radio node <NUM>-B); and communications to/from end-user nodes supported by the remote radio node (e.g. the second radio node <NUM>-B) from/to other devices in the core network (e.g. end-user nodes supported by other radio nodes).

Each radio node <NUM>-A, <NUM>-B comprises a first radio unit <NUM>-A, <NUM>-B for transmitting and receiving information using a first frequency bandwidth (FBACKHAUL), a second radio unit <NUM>-A, <NUM>-B for transmitting and receiving information using a second frequency bandwidth (FEND-USER) and a control unit <NUM>-A, <NUM>-B for controlling the operation of the radio node <NUM>-A, <NUM>-B and, in particular, for controlling the operation of the first and second radio units <NUM>-A, <NUM>-B, <NUM>-A, <NUM>-B. Since the first and second radio units are capable of transmitting and receiving radio signals, the first and second radio units <NUM>-A, <NUM>-B, <NUM>-A, <NUM>-B may be referred to as transceivers.

The first and second frequency bandwidths (FBACKHAUL, FEND-USER) are different (i.e. they are not identical). As shown in <FIG> the first and second frequency bandwidths may be disjoint (i.e. non-overlapping). However, in other examples the first and second frequency bandwidths (FBACKHAUL, FEND-USER) may be overlapping. In some cases, the first frequency bandwidth (FBACKHAUL) may fall in any licensed or unlicensed region of the electromagnetic spectrum, such as, but not limited to, the <NUM>-<NUM> frequency band, the V-band, the E-band, the W-band or the D-band; and the second frequency bandwidth (FEND-USER) may be in the region of <NUM> - <NUM> or another frequency band, such as, but not limited to, an E-UTRA frequency allocation. As described in more detail below with reference to <FIG> each radio unit <NUM>-A, <NUM>-B, <NUM>-A, <NUM>-B may comprise, for example, a modem, an RF unit and one or more antennas. However, it will be evident to a person of skill in the art that this is an example only and that the radio units <NUM>-A, <NUM>-B, <NUM>-A, <NUM>-B may comprise additional and/or different components.

The control units <NUM>-A, <NUM>-B are configured to generate and output one or more control signals that cause the corresponding second radio unit <NUM>-A, <NUM>-B to provide uplink <NUM>-A, <NUM>-B and downlink <NUM>-A, <NUM>-B radio access connectivity to one or more end-user nodes <NUM>-A, <NUM>-B using the second frequency bandwidth (FEND-USER). Since the second frequency bandwidth is used to provide radio access connectivity to their respective end-user nodes it may be referred to as the end-user frequency bandwidth or the radio access bandwidth. The end-user nodes <NUM>-A, <NUM>-B may be any nomadic, fixed or mobile device capable of establishing a bidirectional wireless communication with the core network <NUM>.

The control units <NUM>-A, <NUM>-B are also configured to generate one or more control signals that cause the corresponding first radio unit <NUM>-A, <NUM>-B to exchange a first portion of the backhaul information with the other radio node <NUM>-B, <NUM>-A over a first communication link <NUM>, <NUM> established using the first frequency bandwidth (FBACKHAUL), and that cause the corresponding second radio unit <NUM>-A, <NUM>-B to exchange a second portion of the backhaul information with the other radio node <NUM>-B, <NUM>-A over a second communication link <NUM>, <NUM> using the second frequency bandwidth (FEND-USER).

Since the first communication link <NUM>, <NUM> is established using a frequency bandwidth (FBACKHAUL) dedicated to exchanging backhaul information the first communication link <NUM>, <NUM> may also be referred to as a dedicated point-to-point radio backhaul link. Similarly, since the second communication link <NUM>, <NUM> is established using the same frequency bandwidth (FEND-USER) that is used to provide uplink and downlink radio access connectivity to the end-user nodes, the second communication link <NUM>, <NUM> may be referred to as an in-band radio backhaul link. As a result, in the example of <FIG> backhaul information is exchanged over both a dedicated point-to-point radio backhaul link (the first communication link <NUM>, <NUM>) and an in-band radio backhaul link (the second communication link <NUM>, <NUM>). Such a configuration allows the in-band radio backhaul link (i.e. the second communication link <NUM>, <NUM>) to act as a complementary backhaul link to the dedicated point-to-point radio backhaul link (i.e. the first communication link <NUM>, <NUM>).

This allows the design constraints on the dedicated point-to-point radio backhaul link (e.g. the first communication link <NUM>, <NUM>) to be relaxed compared to systems, such as system <NUM> of <FIG>, which use only a single dedicated point-to-point radio backhaul link for exchanging backhaul information. For example, in a system, such as the system <NUM> of <FIG>, with a single dedicated point-to-point radio backhaul link, the single dedicated point-to-point radio backhaul link may be overengineered so as to guarantee a minimum throughput for a certain percentage of time (e.g. the minimum throughput will be achieved <NUM>% of the time - commonly referred to as a "five nines" guarantee). This means that the single dedicated point-to-point radio backhaul link may be overengineered so that it can provide the guaranteed throughput even in conditions (e.g. certain weather conditions) that adversely affect the quality of the link. Using two backhaul links, the dedicated point-to-point radio backhaul link and the in-band backhaul link (i.e. the first and second communication links), together means that the same guaranteed minimum throughput for a certain percentage of time may be achieved, but with the dedicated point-to-point backhaul link itself providing a lower guaranteed throughput. This allows the dedicated point-to-point backhaul link to be implemented under less restrictions.

Alternatively, if the same constraints are placed on the dedicated point-to-point radio backhaul link (e.g. the first communication link <NUM>, <NUM>) to guarantee a minimum throughput for a certain percentage of time (e.g. <NUM>%) then a higher guaranteed throughput for the same percentage of time (e.g. <NUM>%) may be able to be achieved with the same dedicated point-to-point radio backhaul link as additional throughput is provided by the in-band backhaul link (e.g. the second communication link <NUM>, <NUM>).

Furthermore, since there are two backhaul links that have different or diverse characteristics the control units <NUM>-A, <NUM>-B may decide which backhaul information is sent over the first communication link <NUM>, <NUM> and which backhaul information is sent over the second communication link <NUM>, <NUM> based on the characteristics of the first and second communication links <NUM>, <NUM>, <NUM>, <NUM>. For example, the backhaul information may comprise a plurality of subsets of backhaul information wherein each subset is associated with a priority and the determination of which subset(s) are sent over the first communication link <NUM>, <NUM> and which subset(s) are sent over the second communication link <NUM>, <NUM> is based on the priorities associated with the subsets. For example, the higher priority subset(s) may be sent over the communication link that has lower latency.

The control units <NUM>-A, <NUM>-B of the first and second radio nodes <NUM>-A, <NUM>-B work in a synchronized manner to ensure, for example, that, when one control unit <NUM>-A configures the corresponding second radio unit <NUM>-A to establish the second communication link, the other control unit <NUM>-B also configures the corresponding second radio unit <NUM>-B to establish the second communication link. In some examples, as described with reference to <FIG>, the radio nodes <NUM>-A, <NUM>-B, or the control units <NUM>-A, <NUM>-B, may comprise a synchronization unit that is configured to obtain synchronization information (e.g. Global Navigation Satellite System (GNSS) signals) to ensure that the radio nodes are time synchronized. In other examples the radio nodes <NUM>-A, <NUM>-B, or the control units <NUM>-A, <NUM>-B, may be synchronized through a distributed network synchronization protocol such as, but not limited to, the IEEE <NUM> Precision Time Protocol.

In some cases, the control units <NUM>-A, <NUM>-B may be configured to dynamically adjust the amount or portion of the second frequency bandwidth (FEND-USER) that is used to establish the second communication link <NUM>, <NUM> based, at least, on a determined quality of the first communication link <NUM>, <NUM>.

In an embodiment, the control units <NUM>-A, <NUM>-B are configured to allocate none of the second frequency bandwidth (FEND-USER) for use in establishing the second communication link <NUM>, <NUM> when the quality of the first communication link <NUM>, <NUM> is equal to or greater than a minimum quality, and to allocate at least a portion of the second frequency bandwidth (FEND-USER) for use in establishing the second communication link <NUM>, <NUM> when the quality of the first communication link <NUM>, <NUM> is less than the minimum quality. In other words, in some cases, the control units <NUM>-A, <NUM>-B may be configured to cause the second communication link <NUM>, <NUM> to be dynamically established if the quality of the first communication link <NUM>, <NUM> is less than a minimum quality. This allows the second communication link <NUM>, <NUM> to act as a backup to the first communication link <NUM>, <NUM> wherein the second communication link <NUM>, <NUM> is established when, for example, the first communication link <NUM>, <NUM> cannot itself provide a certain throughput. This allows the second frequency bandwidth (FEND-USER) to be entirely dedicated to providing uplink <NUM>-A, <NUM>-B and downlink <NUM>-A, <NUM>-B radio access connectivity to the end-user nodes <NUM>-A, <NUM>-B when the second communication link is not needed.

If a control unit <NUM>-A, <NUM>-B determines that at least a portion of the second frequency bandwidth (FEND-USER) is to be allocated for use in establishing the second communication link <NUM>, <NUM> then the control unit <NUM>-A, <NUM>-B determines the amount or portion of the second frequency bandwidth (FEND-USER) to be used in establishing the second communication link <NUM>, <NUM> (i.e. the amount of the second frequency bandwidth (FEND-USER) dedicated to exchanging backhaul information) based on the quality of the first communication link <NUM>, <NUM>; or as an example one or more of: system requirements (e.g. target throughputs); the status or quality of the second communication link <NUM>, <NUM>; and the status or quality of the end-user uplinks <NUM>-A, <NUM>-B and downlinks <NUM>-A, <NUM>-B. For example, the control units <NUM>-A, <NUM>-B may determine the amount or portion of the second frequency bandwidth (FEND-USER) to be used in establishing the second communication link <NUM>, <NUM> based on one or more of:.

As is known to those of skill in the art the spectral efficiency of a communication link is the information rate that can be transmitted over a given bandwidth. The link spectral efficiency is typically measured in bits/s/Hz. It is the net bit rate or maximum throughput divided by the bandwidth in Hz of a communication link.

The control units <NUM>-A, <NUM>-B may be configured to allocate none, a portion, or all of the second frequency bandwidth (FEND-USER) for establishing the second communication link <NUM>, <NUM> by time partitioning radio access frames for the second frequency bandwidth (FEND-USER) into a plurality of epochs and by outputting one or more control signals to cause the corresponding second radio unit <NUM>-A, <NUM>-B to perform one or more of the following in each of the plurality of epochs based on at least the quality of the first communication link: provide uplink <NUM>-A, <NUM>-B radio access connectivity to one or more of its end-user nodes <NUM>-A, <NUM>-B using the second frequency bandwidth (FEND-USER); provide downlink <NUM>-A, <NUM>-B radio access connectivity to one or more of its end-user nodes <NUM>-A, <NUM>-B using the second frequency bandwidth (FEND-USER); transmit backhaul information to the other radio node <NUM>-B, <NUM>-A using the second frequency bandwidth (FEND-USER); and receive backhaul information from the other radio node <NUM>-B, <NUM>-A using the second frequency bandwidth (FEND-USER). Examples of how a radio access frame may be partitioned into a plurality of epochs will be described below with reference to <FIG>.

The term "epoch" is used herein to mean a period of time. Accordingly, time partitioning a radio access frame into a plurality of epochs comprises dividing the radio access frame into a plurality of smaller time periods. Dividing radio access frames for the second frequency bandwidth (FEND-USER) into a plurality of epochs and then controlling what action (uplink, downlink, backhaul transmit, backhaul receive) the second radio unit <NUM>-A, <NUM>-B performs via the second frequency bandwidth (FEND-USER) in each epoch controls how much of the second frequency bandwidth is allocated to each action (uplink, downlink, backhaul transmit, backhaul receive) and thus how much of the second frequency bandwidth is allocated for establishing the second communication link (i.e. for transmitting and receiving backhaul information).

Specifically, as described in more detail below, the duration of the epochs determines or controls the radio access connectivity throughput and the backhaul throughput. In particular, the duration of the epochs determines or controls the uplink radio access connectivity throughput provided by the radio nodes to the end-user nodes, the downlink radio access connectivity throughput provided by the radio nodes to the end-user nodes, the transmit backhaul throughput and the receive backhaul throughput. Accordingly the control units <NUM>-A, <NUM>-B may be configured to select the duration of the epochs to maximize a function of one or more of: the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes; the total downlink radio access connectivity throughput provided to the end-user nodes by the remote radio node (e.g. the second radio node <NUM>-B); the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B; and the total throughput of backhaul information transmitted from the second radio node <NUM>-B to the first radio node <NUM>-A. The maximization may be performed under one or more constraints to ensure a minimum throughput is provided for uplink/downlink access connectivity and/or backhaul information.

The control units <NUM>-A, <NUM>-B may be implemented in software or hardware. For example, one or more of the control units <NUM>-A, <NUM>-B may be a computing device that comprises one or more processors wherein the one or more processors are configured to generate and output the control signals to control the operation of the first and second radio units <NUM>-A, <NUM>-B, <NUM>-A, <NUM>-B. Specifically, in these examples the one or more processors may be configured to generate and output the control signals to cause the first and second radio units to exchange backhaul information with another radio unit and provide uplink and downlink radio access connectivity to one or more end-user nodes using the first and second frequency bandwidths (FBACKHAUL and FEND-USER) as described above. The one or more processors may also be configured to dynamically allocate none or a portion of the second frequency bandwidth (FEND-USER) for use in establishing the second communication link as described above. A processor may be any kind of general purpose or dedicated processor, such as a central processing unit (CPU), System-on-chip, state machine, media processor, an application-specific integrated circuit (ASIC), a programmable logic array, a field-programmable gate array (FPGA), or the like.

Although the system of <FIG> shows that each radio node <NUM>-A, <NUM>-B comprises a control unit <NUM>-A, <NUM>-B which controls the operation of that radio node (and specifically the operation of the first and second radio units of that radio node), in other examples, the control units <NUM>-A, <NUM>-B may not form part of the radio nodes <NUM>-A, <NUM>-B, but may be in communication with the radio nodes to control operation thereof. In yet other examples there may be a single control unit that is remote from, but in communication with, the radio nodes <NUM>-A, <NUM>-B and performs the functions of the two control units <NUM>-A, <NUM>-B to control operation of both radio nodes <NUM>-A, <NUM>-B. For example, a single control unit may generate control signals to control the operation of the first and second radio units <NUM>-A, <NUM>-B, <NUM>-A, <NUM>-B of both the first and second radio nodes <NUM>-A, <NUM>-B.

Although the system of <FIG> comprises only two radio nodes <NUM>-A, <NUM>-B it will be evident to a person of skill in the art that the methods, principles and techniques described herein may be applied to systems with more than two radio nodes each providing uplink and downlink radio access connectivity to their respective end-user nodes over a second frequency bandwidth (FEND-USER) and connected to one other node through a first communication link that is established using a first frequency bandwidth (FBACKHAUL) wherein backhaul information is exchanged between that node and the other node over the first communication link and a second communication link established using the second frequency bandwidth (FEND-USER).

Although the system of <FIG> shows the first and second radio units <NUM>-A, <NUM>-A, <NUM>-B, <NUM>-B of a particular radio node <NUM>-A, <NUM>-B as being separate and distinct units, in other examples the functions that are performed by the first and second radio units <NUM>-A, <NUM>-A, <NUM>-B, <NUM>-B of a radio node <NUM>-A, <NUM>-B may be performed by a single radio unit of the radio node <NUM>-A, <NUM>-B that is capable of transmitting and receiving data over the first frequency bandwidth (FBACKHAUL) and the second frequency bandwidth (FEND-USER).

Reference is now made to <FIG> which illustrates an example method <NUM> for dynamically allocating none or a portion of the second frequency bandwidth for use in establishing the second communication link. In other words, the example method <NUM> is for dynamically determining whether to establish the second communication link <NUM>, <NUM>, and if so, how much (or what portion) of the second frequency bandwidth (FEND-USER) is to be used to establish the second communication link (i.e. how much (or what portion) of the second frequency bandwidth (FEND-USER) is to be dedicated to exchanging backhaul information). The method <NUM> may be implemented by the control unit <NUM>-A, <NUM>-B.

The method <NUM> begins at block <NUM> where the control unit <NUM>-A, <NUM>-B determines whether the quality of the first communication link is greater than or equal to a minimum quality. In some cases, the control unit <NUM>-A, <NUM>-B may be configured to determine that the quality of the first communication link <NUM>, <NUM> is greater than or equal to a minimum quality in response to determining that a throughput of backhaul information transmitted in one direction (e.g. the throughput of backhaul information transmitted from the first radio node <NUM>-A over the first communication link <NUM> ( <MAT>)) is greater than or equal to a first threshold (β<NUM>) as shown in equation (<NUM>), and that a throughput of backhaul information transmitted in the other direction (e.g. the throughput of backhaul information received by the first radio node <NUM>-A over the first communication link <NUM> ( <MAT>)) is greater than or equal to a second threshold (β<NUM>) as shown in equation (<NUM>): <MAT> <MAT>.

In some cases, the first threshold (β<NUM>) may be generated (e.g. by the control units <NUM>-A, <NUM>-B) to represent a function of the downlink spectral efficiencies provided by the second radio node <NUM>-B (i.e. the remote radio node) over the second frequency bandwidth (FEND-USER) while the second threshold (β<NUM>) may be generated (e.g. by the control units <NUM>-A, <NUM>-B) to represent a function of the uplink spectral efficiencies provided by the second radio node <NUM>-B (i.e. the remote radio node) over the second frequency bandwidth (FEND-USER). The spectral efficiencies may be averaged over an arbitrary time basis and may be acquired either through direct measurement or synthetically computed from formulas that rely on knowledge of the uplinks and downlinks connecting the second radio node <NUM>-B to its end-user nodes <NUM>-B (e.g. A8) and statistics of the network interference levels (e.g. A9).

In some cases, the control unit <NUM>-A, <NUM>-B may be configured to directly measure the backhaul information throughputs over the first communication link <NUM>, <NUM> ( <MAT>, <MAT>) based on, for example, information from the first radio unit <NUM>-A, <NUM>-B. In other cases, the control unit <NUM>-A, <NUM>-B may be configured to obtain information (such as, but not limited to, statistics) on the backhaul information throughputs over the first communication link from another component or device in the system. It will be evident that this is an example only and that the control unit <NUM>-A, <NUM>-B may be configured to determine that the quality of the first communication link <NUM>, <NUM> is less than a minimum quality in another manner.

If the control unit <NUM>-A, <NUM>-B determines at block <NUM> that the quality of the first communication link <NUM>, <NUM> is greater than or equal to a minimum quality then the method <NUM> proceeds to block <NUM>. If, however, the control unit <NUM>-A, <NUM>-B determines at block <NUM> that the quality of the first communication link <NUM>, <NUM> is less than the minimum quality then the method <NUM> proceeds to block <NUM>.

At block <NUM>, since it has been determined that the quality of the first communication link is greater than or equal to a minimum quality, the backhaul information between the first and second radio nodes can be sufficiently exchanged using the first communication link only. Accordingly, the control unit <NUM>-A, <NUM>-B allocates none of the second frequency bandwidth (FEND-USER) to establishing the second communication link <NUM>, <NUM>. In other words, in this case the second communication link is not established. The control unit <NUM>-A, <NUM>-B then partitions the radio access frames for the second frequency bandwidth (FEND-USER) into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to only provide uplink and downlink radio access connectivity to their respective end-user nodes <NUM>-A, <NUM>-B over the second frequency bandwidth (FEND-USER). For example, the control unit may partition the radio access frame to enable the radio nodes <NUM>-A, <NUM>-B to provide standard uplink and downlink operation. An example of how the radio access frame may be partitioned to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to the end-user nodes using the second frequency bandwidth (FEND-USER) will be described below with reference to <FIG>. Once the radio access frame for the second frequency bandwidth (FEND-USER) has been partitioned the method <NUM> ends.

At block <NUM>, since it has been determined that the quality of the first communication link is less than the minimum quality, the backhaul information cannot be sufficiently exchanged over the first communication link alone thus at least a portion of the second frequency bandwidth is allocated to establish the second communication link. To allocate a portion of the second frequency bandwidth for establishing the second communication link the radio access frame is partitioned into a plurality of epochs so that the radio nodes use the second frequency bandwidth to both provide uplink and downlink connectivity access to end-user nodes and exchange backhaul information. To determine how to partition the radio access frames the control unit <NUM>-A, <NUM>-B determines whether the second radio unit <NUM>-A, <NUM>-B supports spatial multiplexing. This is because the frame can be partitioned in a different manner if the second radio unit supports spatial multiplexing. As is known to those of skill in the art, spatial multiplexing (SM) is a transmission technique in multiple-input-multiple-output (MIMO) wireless systems used to transmit independent and separately encoded data signal (which may be referred to as streams) from multiple transmit antennas simultaneously or in parallel using a known spatial multiplexing technique.

If it is determined at block <NUM> that the second radio unit <NUM>-A, <NUM>-B does not support spatial multiplexing then the method <NUM> proceeds to block <NUM>. If, however, it is determined at block <NUM> that the second radio unit does support spatial multiplexing then the method <NUM> proceeds to block <NUM>.

At block <NUM>, the control unit <NUM>-A, <NUM>-B time partitions the radio access frames for the second frequency bandwidth (FEND-USER) into a plurality of epochs to enable the radio nodes to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) without using spatial multiplexing techniques. An example of how the radio access frame for the second frequency bandwidth (FEND-USER) may be partitioned to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to the end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) without spatial multiplexing is described below with reference to <FIG>. Once the radio access frame for the second frequency bandwidth (FEND-USER) has been partitioned the method <NUM> ends.

At block <NUM>, the control unit <NUM>-A, <NUM>-B time partitions the radio access frames over the second frequency bandwidth (FEND-USER) into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) using spatial multiplexing techniques. Examples of how the radio access frame for the second frequency bandwidth (FEND-USER) may be partitioned to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to the end-user nodes and exchange backhaul information using the second frequency bandwidth (FEND-USER) with spatial multiplexing techniques are described below with reference to <FIG> and <FIG>. Once the radio access frame for the second frequency bandwidth (FEND-USER) has been partitioned the method <NUM> ends.

When the second frequency bandwidth (FEND-USER) is operated in a Time Division Duplexing (TDD) mode (i.e. when transmissions and receptions over the second frequency bandwidth (FEND-USER) at a given radio node occur over different time slots in the same frequency bandwidth) the method can be as described above. However, when the second frequency bandwidth (FEND-USER) is operated in a Frequency Division Duplexing (FDD) mode (i.e. when transmissions and receptions at a given radio node occur over different frequency allocations within the second frequency bandwidth (FEND-USER)) the method may comprise, in addition to allocating time resources (via different epochs) to provide uplink and downlink radio access connectivity and exchange backhaul information over the second frequency bandwidth (FEND-USER), allocating frequency resources from the second frequency bandwidth to provide uplink and downlink radio access connectivity and exchange backhaul information.

In some cases, the control units <NUM>-A, <NUM>-B may be configured to execute method <NUM> periodically. For example, in some cases the control units <NUM>-A, <NUM>-B may be configured to execute method <NUM> after a predetermined number (e.g. N where N is an integer greater than or equal to two) of radio access frames.

Reference is now made to <FIG> which illustrates an example of how the radio access frame for the second frequency bandwidth (FEND-USER) is partitioned (e.g. in block <NUM> of method <NUM> of <FIG>) into a plurality of epochs to only provide uplink and downlink radio access connectivity to the end-user nodes over the second frequency bandwidth (FEND-USER).

Since the second frequency bandwidth is only used to provide uplink and downlink radio access, the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) is equal to the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the first communication link ( <MAT>) as shown in equation (<NUM>) and the total throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B (TBHB→A) is equal to the throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the first communication link ( <MAT>) as shown in equation (<NUM>): <MAT> <MAT>.

Time partitioning the radio access frame for the second frequency bandwidth into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to only provide uplink and downlink radio access connectivity to the end-user nodes over the second frequency bandwidth (FEND-USER) may comprise the control unit time partitioning the radio access frame <NUM> for the second frequency bandwidth (FEND-USER) into two epochs <NUM>, <NUM>. The control unit <NUM>-A, <NUM>-B then causes the corresponding second radio unit <NUM>-A, <NUM>-B to provide downlink <NUM>-A, <NUM>-B radio access connectivity to its end-user nodes in one epoch <NUM> (αDL) (which may be referred to as the downlink epoch); and provide uplink <NUM>-A, <NUM>-B radio access connectivity to its end-user nodes in the other epoch <NUM> (αUL) (which may be referred to as the uplink epoch). The durations of the epochs <NUM>, <NUM> (αDL, αUL) may be selected by the control units <NUM>-A, <NUM>-B to reflect the downlink and uplink imbalance that is imposed by the radio access protocol implemented by the radio node. Although <FIG> illustrates that the whole frame duration (αtotal) falls into one epoch or the other (i.e. αtotal = αDL + αUL), in other cases guard periods may be inserted between the epochs wherein neither uplink nor downlink radio access connectivity is provided to the end-user nodes.

Reference is now made to <FIG> which illustrates an example of a how a radio access frame for the second frequency bandwidth (FEND-USER) is time partitioned into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to the end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) without spatial multiplexing techniques being supported by the radio nodes <NUM>-A, <NUM>-B (e.g. in block <NUM> of method <NUM> of <FIG>).

Since the first communication link <NUM>, <NUM> is not sufficient to meet the backhaul information needs, at least a portion of the second frequency bandwidth (FEND-USER) is allocated for establishing the second communication link <NUM>, <NUM> so that a first portion of the backhaul information is exchanged via the first communication link <NUM>, <NUM> over the first frequency bandwidth and a second portion of the backhaul information is exchanged via the second communication link <NUM>, <NUM> over the second frequency bandwidth. The first portion of the backhaul information may correspond to the amount of backhaul information that can be reliably carried over the first communication link using the first frequency bandwidth and the second part of the backhaul information may correspond to the amount of backhaul information that can be reliably carried over the second communication link using the second frequency bandwidth.

To enable transmission and receipt of backhaul information over the second frequency bandwidth the radio frame is divided into more epochs than in the example shown in <FIG>. Specifically, there must be at least two additional epochs to allow the second radio unit <NUM>-A, <NUM>-B to transmit and receive backhaul information using the second frequency bandwidth in addition to providing uplink and downlink radio access connectivity to its one or more end-user nodes.

In one example, the control unit <NUM>-A, <NUM>-B may be configured to partition the radio access frames for the second frequency bandwidth (FEND-USER) into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) by time partitioning the radio access frame <NUM> for the second frequency bandwidth (FEND-USER) into four epochs <NUM>, <NUM>, <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>). The control units <NUM>-A, <NUM>-B then cause the corresponding second radio unit <NUM>-A, <NUM>-B to:.

Although the epochs are shown in a particular order - e.g. the backhaul transmit epoch is the first epoch, the backhaul receive epoch is the second epoch, the downlink epoch is the third epoch and the uplink epoch is the fourth epoch- it will be evident to a person of skill in the art that the different epochs may be implemented in a different order in the radio frame. For example, in another example, the downlink epoch may be the first epoch, the uplink epoch the second epoch, the backhaul receive epoch the third epoch and the backhaul transmit epoch the fourth epoch.

In this example, the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) is equal to the sum of the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the first communication link ( <MAT>) and the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the second communication link ( <MAT>) as shown in equation (<NUM>); and the total throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B (TBHB→A) is equal to the sum of the throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the first communication link <MAT> and the throughput of the backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the second communication link ( <MAT>) as shown in equation (<NUM>): <MAT> <MAT>.

The control units <NUM>-A, <NUM>-B may be configured to select the duration of the epochs <NUM>, <NUM>, <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>) so as to maximize or optimize a function of one or more of: the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes ( <MAT>); the total downlink radio access connectivity throughput provided to the end-user nodes by the remote radio node (e.g. the second radio node <NUM>-B) ( <MAT>); the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B); and the total throughput of backhaul information transmitted from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A). Such a function is illustrated in equation (<NUM>): <MAT>.

As is known to those of skill in the art, maximizing a function of one or more variables comprises identifying the values of the one or more variables which result in a maximum value of the function. In other words, the control units <NUM>-A, <NUM>-B may be configured to select the duration of the epochs <NUM>, <NUM>, <NUM>, <NUM> that generates a maximum value of a function of one or more of the above-noted variables (e.g. <MAT>, TBHA→B,TBHB→A). The set of values for the one or more variables which result in a maximum value of the function may be referred to as the optimal solution. The control units <NUM>-A, <NUM>-B may be configured to maximize the function using any known methods for maximizing or optimizing a function such as, but not limited to, systematically choosing values for the one or more variables from an allowed set, computing the value of the function, and then selecting the values for the one or more variables that produce the maximum value of the function.

The maximization may be subjected to one or more constraints (which is referred to as constrained maximization or optimization). For example, the maximization may be under the constraint that the total uplink and downlink radio access connectivity throughputs provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes ( <MAT>) can be backhauled over the first and second communication links <NUM>, <NUM>, <NUM>, <NUM>. For example, the maximization may be under the constraint that the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) is greater than or equal to the total downlink radio access connectivity throughput provided by the second radio node <NUM>-B to its end-user nodes ( <MAT>) as shown in equation (<NUM>); and/or the constraint that the total throughput of backhaul information transmitted from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A) is greater than or equal to the total uplink radio access connectivity throughput provided by the second radio node <NUM>-B to its end-user nodes ( <MAT>) as shown in equation (<NUM>): <MAT> <MAT>.

The maximization may also, or alternatively, be under the constraint that the uplink and/or downlink throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes <NUM>-B does not fall below a predetermined threshold (which may be the same or different for the uplink and downlink throughputs). For example, the maximization may be under the constraint that the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes <NUM>-B ( <MAT>) is greater than or equal to a predetermined threshold (γ<NUM>) as shown in equation (<NUM>); and/or the constraint that the total downlink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes <NUM>-B ( <MAT>) is greater than or equal to a threshold (γ<NUM>) as shown in equation (<NUM>): <MAT> <MAT>.

The maximization may also, or alternatively, be under the constraint that the uplink and/or downlink throughput provided by the anchor radio node (e.g. the first radio node <NUM>-A) to its end-user nodes <NUM>-A does not fall below a predetermined threshold (which may be the same or different for the uplink and downlink throughputs). For example, the maximization may be under the constraint that the total uplink radio access connectivity throughput provided by the first radio node <NUM>-A to its end-user nodes <NUM>-A ( <MAT>) is greater than or equal to a predetermined threshold (γ<NUM>) as shown in equation (<NUM>); and/or the constraint that the total downlink radio access connectivity throughput provided by the first radio node <NUM>-A to its end-user nodes <NUM>-A ( <MAT>) is greater than or equal to a threshold (γ<NUM>) as shown in equation (<NUM>): <MAT> <MAT>.

The maximization may also, or alternatively, be under the constraint that the combined duration of the four disjointed epochs <NUM>, <NUM>, <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>) is equal to the total duration (∝total) of the radio access frame for the second frequency bandwidth (FEND-USER) as shown in equation (<NUM>): <MAT>.

The thresholds γ<NUM>, γ<NUM>, γ<NUM>, γ<NUM> are generally based on a minimum quality of service rate to be achieved for the end-user nodes. The thresholds γ<NUM>, γ<NUM> related to the radio access connectivity provided by the remote radio node (e.g. the second radio node <NUM>-B) may be a function of the uplink and/or downlink overall access spectral efficiencies provided by the second radio node <NUM>-B during standard network operation over the second frequency bandwidth (FEND-USER). The thresholds γ<NUM>, γ<NUM> related to the radio access connectivity provided by the anchor radio node (e.g. the first radio node <NUM>-A) may be a function of the uplink and/or downlink overall access spectral efficiencies provided by the first radio node <NUM>-A during standard network operation over the second frequency bandwidth (FEND-USER). The thresholds γ<NUM>, γ<NUM>, γ<NUM>, γ<NUM> may be predefined (e.g. fixed) or they may be dynamically adjusted. The thresholds γ<NUM>, γ<NUM>, γ<NUM>, γ<NUM> may be manually provided to the control units <NUM>-A, <NUM>-B, for example by a user or administrator, or they may be hard-coded into the control units <NUM>-A, <NUM>-B.

The uplink, downlink, and backhaul throughputs ( <MAT>, TBHA→B,TBHB→A) achieved will depend on the duration of the epochs and may be determined or estimated from direct measurements of the system spectral efficiencies and/or throughputs (e.g. A1, A2, A3, A4, A5 and A6) or may be determined or estimated from known formulas that are based on knowledge of the communication links connecting the radio nodes (e.g. A7), the communication channels between the radio nodes <NUM>-A, <NUM>-B and the end-user nodes <NUM>-A, <NUM>-B (e.g. A8), and statistics of the interference levels experienced by the radio nodes and the end-user nodes (e.g. A9 and A10).

The function that is maximized may be any linear or non-linear function based on the input variables (e.g. the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes; the total downlink radio access connectivity throughput provided to the end-user nodes by the remote radio node (e.g. the second radio node <NUM>-B); the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node; and the total throughput of backhaul information transmitted from the second radio node to the first radio node <NUM>-A). For example, the function that is maximized may be a weighted linear combination of the uplink and downlink radio access connectivity throughputs that are provided by the remote radio node (e.g. the second radio node <NUM>-B) ( <MAT>). In another example, the function that is maximized may be a weighted linear combination of the overall backhaul information throughput from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) and the overall backhaul information throughput from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A). In yet another example, the function that is maximized is a weighted linear combination of the uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) ( <MAT>), the downlink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) ( <MAT>), the overall backhaul information throughput from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) and the overall backhaul information throughput from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A). However, it will be evident to a person of skill in the art that this is an example only and that other functions may be used to determine the duration of the epochs.

Reference is now made to <FIG> which illustrates a first example of how a radio access frame for the second frequency bandwidth (FEND-USER) may be time partitioned into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) when spatial multiplexing techniques are supported by the radio nodes <NUM>-A, <NUM>-B (e.g. in block <NUM> of the method <NUM> of <FIG>).

As described above, in this case the first communication link <NUM>, <NUM> is not sufficient to meet the backhaul information needs and so at least a portion of the second frequency bandwidth (FEND-USER) is allocated for establishing the second communication link <NUM>, <NUM> so that a first portion of the backhaul information is exchanged via the first communication link using the first frequency bandwidth and a second portion of the backhaul information is exchanged via the second communication link using the second frequency bandwidth. The first portion of the backhaul information may correspond to the amount of backhaul information that can be reliably carried over the first communication link using the first frequency bandwidth and the second portion of the backhaul information may correspond to the amount of backhaul information that can be reliably carried over the second communication link using the second frequency bandwidth.

Since the second radio units <NUM>-A, <NUM>-B support spatial multiplexing, the second radio units can concurrently or simultaneously receive two or more different information streams over the second frequency bandwidth, and/or concurrently transmit two or more different information streams over the second frequency bandwidth. This allows each second radio unit <NUM>-A, <NUM>-B to concurrently provide uplink radio access connectivity to its end-user nodes using the second frequency bandwidth (FEND-USER) and receive backhaul information from the other radio node using the second frequency bandwidth (FEND-USER), and/or concurrently provide downlink radio access connectivity to its end-user nodes using the second frequency bandwidth (FEND-USER) and transmit backhaul information to the other radio node using the second frequency bandwidth (FEND-USER).

Accordingly, where the second radio units <NUM>-A, <NUM>-B support spatial multiplexing, the control units <NUM>-A, <NUM>-B may be configured to divide the radio access frame <NUM> for the second frequency bandwidth (FEND-USER) into at least two epochs <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>). The control units <NUM>-A, <NUM>-B then cause their corresponding second radio unit <NUM>-A, <NUM>-B to:.

As described above, the control units work in a synchronized manner so that when one radio node is configured to transmit backhaul information over the second frequency bandwidth the other radio node is configured to receive backhaul information over the second frequency bandwidth and vice versa.

It is noted that in the example of <FIG> the uplink radio transmissions from the end-user nodes <NUM>-B connected to the second radio node <NUM>-B may interfere with the downlink radio transmissions to the end-user nodes <NUM>-A connected to the first radio node <NUM>-A. Similarly, the uplink radio transmissions from the end-user nodes <NUM>-A connected to the first radio node <NUM>-A may interfere with the downlink radio transmissions to the end-user nodes <NUM>-B connected to the second radio node <NUM>-B. Accordingly, the control units <NUM>-A, <NUM>-B may be configured to account for these interference levels (e.g. A9) in the maximization of the function set out in equation (<NUM>).

Although the epochs are shown in a particular order in <FIG> - e.g. the epoch in which the second radio unit <NUM>-A of the first radio node <NUM>-A concurrently provides downlink radio access connectivity to its end-user nodes and transmits backhaul information is the first epoch - it will be evident to a person of skill in the art that the different epochs may be implemented in a different order in the radio frame. For example, the epoch in which the second radio unit <NUM>-A of the first radio node <NUM>-A concurrently provides downlink radio access connectivity to its end-user nodes and transmits backhaul information may alternatively be the second epoch.

Accordingly, the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) is equal to the sum of the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the first communication link ( <MAT>) and the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the second communication link ( <MAT>) as shown in equation (<NUM>); and the total throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B (TBHB→A) is equal to the sum of the throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the first communication link ( <MAT>) and the throughput of the backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the second communication link ( <MAT>) as shown in equation (<NUM>): <MAT> <MAT>.

Like the example described above with reference to <FIG>, the control units <NUM>-A, <NUM>-B may be configured to select the duration of the epochs <NUM>, and <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>) so as to maximize a function of one or more of: the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes ( <MAT>); the total downlink radio access connectivity throughput provided to the end-user nodes by the remote radio node (e.g. the second radio node <NUM>-B) ( <MAT>); the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B); and the total throughput of backhaul information transmitted from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A) (e.g. as shown in equation (<NUM>)).

Like the example described above with reference to <FIG>, the maximization may be subjected to one or more constraints such as, but not limited to, the constraints described above in reference to <FIG> with respect to equations (<NUM>), (<NUM>), (<NUM>), (<NUM>), (<NUM>), and (<NUM>). The maximization may also, or alternatively, be under the constraint that the combined duration of the two disjointed epochs <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>) is equal to the total duration (∝total) of the radio access frame for the second frequency bandwidth (FEND-USER) as shown in equation (<NUM>): <MAT>.

Reference is now made to <FIG> which illustrates a second example of how a radio access frame for the second frequency bandwidth (FEND-USER) is time partitioned into a plurality of epochs to enable the radio nodes <NUM>-A, <NUM>-B to provide uplink and downlink radio access connectivity to their respective end-user nodes and exchange backhaul information over the second frequency bandwidth (FEND-USER) when spatial multiplexing techniques are supported by the radio nodes <NUM>-A, <NUM>-B (e.g. in block <NUM> of the method <NUM> of <FIG>). In this example, the control units <NUM>-A, <NUM>-B time partition the radio access frame for the second frequency bandwidth (FEND-USER) into four disjoint (i.e. non-overlapping) epochs <NUM>, <NUM>, <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>).

The control units <NUM>-A, <NUM>-B are then configured to cause their corresponding second radio unit <NUM>-A, <NUM>-B to:.

Although the different types of epochs are shown in <FIG> in a particular order - e.g. the epoch in which the second radio unit <NUM>-A of the first radio node <NUM>-A concurrently provides downlink radio access connectivity to its end-user nodes and transmits backhaul information is the first epoch- it will be evident to a person of skill in the art that the different epochs may be implemented in a different order in the radio frame. For example, the epoch in which the second radio unit <NUM>-A of the first radio node <NUM>-A concurrently provides downlink radio access connectivity to its end-user nodes and transmits backhaul information may alternatively be the second epoch.

In this example, like the examples described above with respect to <FIG> and <FIG>, the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) is equal to the sum of the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the first communication link ( <MAT>) and the throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B over the second communication link ( <MAT>) during the first epoch <NUM> (∝<NUM>-<NUM>) as shown in equation (<NUM>); and the total throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B (TBHB→A) is equal to the sum of the throughput of backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the first communication link ( <MAT>) and the throughput of the backhaul information received by the first radio node <NUM>-A from the second radio node <NUM>-B over the second communication link ( <MAT>) during the second epoch <NUM> (∝<NUM>-<NUM>) as shown in equation (<NUM>): <MAT> <MAT>.

Similar to the examples described above with respect to <FIG> and <FIG>, in this example the control units <NUM>-A, <NUM>-B may be configured to select the duration of the epochs <NUM>, <NUM>, <NUM>, <NUM> (∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>, ∝<NUM>-<NUM>) so as to maximize a function of one or more of: the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes ( <MAT>); the total downlink radio access connectivity throughput provided to the end-user nodes by the remote radio node (e.g. the second radio node <NUM>-B) ( <MAT>); the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B); and the total throughput of backhaul information transmitted from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A).

However, in this example since there are two epochs in which uplink radio access connectivity is provided to end-user nodes and two epochs in which downlink radio access connectivity is provided to end-user nodes, the total downlink/uplink radio access connectivity throughput provided to the end-user nodes by the remote radio node (e.g. the second radio node <NUM>-B) is the sum of the downlink/uplink radio access connectivity throughput in each of the relevant epochs. Specifically, the total downlink radio access connectivity throughput provided to the end-user nodes connected to the second radio node <NUM>-B is equal to the sum of the downlink radio access connectivity throughput provided to the end-user nodes connected to the second radio node <NUM>-B in the second epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>) and the downlink radio access connectivity throughput provided to the end-user nodes connected to the second radio node <NUM>-B in the third epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>); and the total uplink radio access connectivity throughput provided to the end-user nodes connected to the second radio node <NUM>-B is equal to the sum of the uplink radio access connectivity throughput provided to the end-user nodes connected to the second radio node <NUM>-B in the first epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>) and the uplink radio access connectivity throughput provided to the end-user nodes connected to the second radio node <NUM>-B in the fourth epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>).

Like the examples described above with respect to <FIG> and <FIG>, the maximization may be subjected to one or more constraints. For example, the maximization may be under the constraint that the total uplink and downlink radio access connectivity throughputs provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes ( <MAT>) can be backhauled over the first and second communication links <NUM>, <NUM>, <NUM>, <NUM>. For example, the maximization may be under the constraint that the total throughput of backhaul information transmitted from the first radio node <NUM>-A to the second radio node <NUM>-B (TBHA→B) is greater than or equal to the total downlink radio access connectivity throughput provided by the second radio node <NUM>-B to its end-user nodes ( <MAT>) as shown in equation (<NUM>); and/or the constraint that the total throughput of backhaul information transmitted from the second radio node <NUM>-B to the first radio node <NUM>-A (TBHB→A) is greater than or equal to the total uplink radio access connectivity throughput provided by the second radio node <NUM>-B to its end-user nodes ( <MAT>) as shown in equation (<NUM>): <MAT> <MAT>.

The maximization may also, or alternatively, be under the constraint that the uplink and/or downlink radio access throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes <NUM>-B does not fall below a predetermined threshold (which may be the same or different for the uplink and downlink throughputs). For example, the maximization may be under the constraint that the total uplink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes ( <MAT>) is greater than or equal to a predetermined threshold (γ<NUM>) as shown in equation (<NUM>); and/or the constraint that the total downlink radio access connectivity throughput provided by the remote radio node (e.g. the second radio node <NUM>-B) to its end-user nodes <NUM>-B ( <MAT>) is greater than or equal to a threshold (γ<NUM>) as shown in equation (<NUM>): <MAT> <MAT>.

The maximization may also, or alternatively, be under the constraint that the uplink and/or downlink throughput provided by the anchor radio node (e.g. the first radio node <NUM>-A) to its end-user nodes <NUM>-A does not fall below a predetermined threshold (which may be the same or different for the uplink and downlink throughputs). In this example since there are two epochs in which uplink radio access connectivity is provided to end-user nodes and two epochs in which downlink radio access connectivity is provided to end-user nodes, the total downlink/uplink radio access connectivity throughput provided to the end-user nodes by the anchor radio node (e.g. the first radio node <NUM>-A) is the sum of the downlink/uplink radio access connectivity throughput in each of the relevant epochs. Specifically, the total downlink radio access connectivity throughput provided to the end-user nodes connected to the first radio node <NUM>-A is equal to the sum of the downlink radio access connectivity throughput provided to the end-user nodes connected to the first radio node <NUM>-A in the first epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>) and the downlink radio access connectivity throughput provided to the end-user nodes connected to the first radio node <NUM>-A in the third epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>); and the total uplink radio access connectivity throughput provided to the end-user nodes connected to the first radio node <NUM>-A is equal to the sum of the uplink radio access connectivity throughput provided to the end-user nodes connected to the first radio node <NUM>-A in the second epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>) and the uplink radio access connectivity throughput provided to the end-user nodes connected to the first radio node <NUM>-A in the fourth epoch <NUM> (∝<NUM>-<NUM>) ( <MAT>).

For example, the maximization may be under the constraint that the total uplink radio access connectivity throughput provided by the first radio node <NUM>-A to its end-user nodes ( <MAT>) is greater than or equal to a predetermined threshold (γ<NUM>) as shown in equation (<NUM>); and/or the constraint that the total downlink radio access connectivity throughput provided by the first radio node <NUM>-A to its end-user nodes ( <MAT>) is greater than or equal to a threshold (γ<NUM>) as shown in equation (<NUM>): <MAT> <MAT>.

Since there are multiple epochs (e.g. epochs <NUM> (∝<NUM>-<NUM>) and <NUM> (∝<NUM>-<NUM>)) in which uplink radio access connectivity is provided by the first radio node <NUM>-A to its end-user nodes <NUM>-A and multiple epochs (e.g. epochs <NUM> (∝<NUM>-<NUM>) and <NUM> (∝<NUM>-<NUM>)) in which downlink radio access connectivity is provided by the first radio node <NUM>-A to its end-user nodes <NUM>-A, where the first radio node <NUM>-A is configured to provide uplink and downlink radio access connectivity to a plurality of end-user nodes <NUM>-A the control unit <NUM>-A may be configured to select the end-user nodes to be allocated or scheduled in the uplink and/or downlink epochs in order to maximize the function described above.

Similarly, since there are multiple epochs (e.g. epochs <NUM> (∝<NUM>-<NUM>) and <NUM> (∝<NUM>-<NUM>)) in which uplink radio access connectivity is provided by the second radio node <NUM>-B to its end-user nodes <NUM>-B and multiple epochs (e.g. epochs <NUM> (∝<NUM>-<NUM>) and <NUM> (∝<NUM>-<NUM>)) in which downlink radio access connectivity is provided by the second radio node <NUM>-B to its end-user nodes <NUM>-B, where the second radio node <NUM>-B is configured to provide uplink and downlink radio access connectivity to a plurality of end-user nodes <NUM>-B the control unit <NUM>-B may be configured to select the end-user nodes to be allocated or scheduled in the uplink and/or downlink epochs in order to maximize the function described above.

For example, the control units <NUM>-A, <NUM>-B may be configured to cause the corresponding second radio unit to provide downlink radio access connectivity to a first subset of the plurality of end-user nodes during one epoch (such as epoch <NUM> (∝<NUM>-<NUM>) for the first radio node <NUM>-A or epoch <NUM> (∝<NUM>-<NUM>) for the second radio node <NUM>-B) and provide downlink radio access connectivity to a different subset of the plurality of end-user nodes in another epoch (such as epoch <NUM> (∝<NUM>-<NUM>)) so as to maximize a function based on one or more of an uplink radio access connectivity throughput provided to the plurality of end-user nodes, a downlink radio access connectivity throughput provided to the plurality of end-user nodes, a throughput of the backhaul information transmitted to the other radio node via the second communication link <NUM>, <NUM> over the second frequency bandwidth, and a throughput of the backhaul information received from the other radio node via the second communication link <NUM>, <NUM> over the second frequency bandwidth.

Similarly, the control units <NUM>-A, <NUM>-B may be configured, in addition, or alternatively, to cause the corresponding second radio unit to provide uplink radio access connectivity to a first subset of the plurality of end-user nodes during one epoch (such as epoch <NUM> (∝<NUM>-<NUM>) for the first radio node <NUM>-A or epoch <NUM> (∝<NUM>-<NUM>) for the second radio node <NUM>-B) and provide uplink radio access connectivity to a different subset of the plurality of end-user nodes in another epoch (such as epoch <NUM> (∝<NUM>-<NUM>)) so as to maximize a function based on one or more of an uplink radio access connectivity throughput provided to the plurality of end-user nodes, a downlink radio access connectivity throughput provided to the plurality of end-user nodes, a throughput of the backhaul information transmitted to the other radio node via the second communication link over the second frequency bandwidth, and a throughput of the backhaul information received from the other radio node via the second communication link over the second frequency bandwidth.

Partitioning the radio access frame as described with respect to <FIG> allows finer control over the downlink and uplink radio access throughput provided to end-user nodes as the uplink access for end-user nodes can be divided between an epoch in which the second frequency bandwidth is dedicated to providing uplink radio access connectivity only and an epoch in which the second frequency bandwidth is used for providing uplink radio access connectivity and receiving backhaul information; and/or the downlink access for end-user nodes can be divided between an epoch in which the second frequency bandwidth is dedicated to providing downlink radio access connectivity only and an epoch in which the second frequency bandwidth is used for providing downlink radio access connectivity and transmitting backhaul information. It also allows a larger portion of the frame (i.e. two epochs) to provide uplink and/or downlink radio access connectivity because spatial multiplexing enables co-existence of backhauling and radio access connectivity over the second frequency bandwidth.

Reference is now made to <FIG> which is a graph <NUM> of the cumulative distribution function of the backhaul information throughput for a conventional microwave backhauling system, such as the system <NUM> of <FIG>, and for a backhauling system <NUM> described herein. Specifically curve <NUM> is the cumulative distribution function of the backhaul information throughput for a conventional microwave backhauling system, such as the system <NUM> of <FIG>, where the backhaul information is transmitted over a single dedicated point-to-point radio backhaul link established over a microwave frequency bandwidth; and curve <NUM> is the cumulative distribution function of the backhaul information throughput for the backhauling system <NUM> described herein where the backhaul information is transmitted jointly over a dedicated point-to-point radio backhaul link established over a microwave frequency bandwidth (FBACKHAUL) and over a second communication link established over the frequency bandwidth (FEND-USER) used to provide uplink and downlink radio access connectivity to the end-user nodes in an adaptive or dynamic manner as described above.

The magnified section <NUM> of <FIG> shows that the backhaul information throughput that is guaranteed for (<NUM> - ε) * <NUM>% amount of the time for the backhauling system <NUM> described herein (indicated at <NUM>) is greater than the backhaul information throughput that is guaranteed for (<NUM> - ε) * <NUM>% amount of the time for a conventional microwave backhauling system (indicated at <NUM>) wherein ε is the normalized probability on the y-axis. Accordingly, the backhauling system <NUM> described herein may increase the backhaul information throughput that is guaranteed for (<NUM> - ε) * <NUM>% amount of the time.

Reference is now made to <FIG> which illustrates a block diagram of an example implementation of the first radio node <NUM>-A. In the example of <FIG> the first radio node <NUM>-A comprises the first radio unit <NUM>-A, the second radio unit <NUM>-A and the control unit <NUM>-A described above. Each radio unit <NUM>-A and <NUM>-A comprises a modem <NUM>, <NUM>, a radio frequency (RF) unit <NUM>, <NUM>, and an antenna unit <NUM>, <NUM> that comprises one or more antenna elements.

As described above, the control unit <NUM>-A generates and outputs one or more control signals which cause the first radio unit <NUM>-A to transmit backhaul information to one or more other radio nodes (e.g. the second radio node <NUM>-B) using the first frequency bandwidth (FBACKHAUL) or cause the first radio unit <NUM>-A to receive backhaul information from another radio node (e.g. the second radio node <NUM>-B) using the first frequency bandwidth (FBACKHAUL).

When the first radio unit <NUM>-A is configured to receive backhaul information from another radio node, an incoming signal <NUM> from another radio node in the first frequency bandwidth (FBACKHAUL) is intercepted by the antenna unit <NUM>. The antenna unit <NUM> then provides the incoming signal to the RF unit <NUM>. The RF unit <NUM> performs well-known RF processing on the incoming signal such as, but limited to, amplification, down-conversion, automatic gain control, filtering and/or any combination thereof. The processed signal is then provided to the modem <NUM> for baseband processing of the signal.

When the first radio unit <NUM>-A is configured to transmit backhaul information to one or more other radio nodes, the modem <NUM> outputs one or more signals that are provided to the RF unit <NUM>. The RF unit <NUM> performs well-known RF operations on the input signals, such as, but not limited to, filtering, up-conversion, amplification, recombination and/or any combination thereof. Accordingly, the RF unit <NUM> may be implemented in hardware by one or more of a filter, up-converter, amplifier, and/or a multiplier. The RF unit <NUM> then provides the processed one or more RF signals to the antenna unit <NUM> which transmits the signals <NUM> using the first frequency bandwidth (FBACKHAUL).

The frequency bandwidth of the received signals <NUM> and/or the transmitted signals <NUM> may have a frequency bandwidth that corresponds to the first frequency bandwidth (FBACKHAUL) or a portion thereof based on the specific frequency planning, duplexing mode and scheduling policy employed. For example, if the first radio unit <NUM>-A implements TDD the totality of the first frequency bandwidth (FBACKHAUL) may be assigned or allocated to both the transmitted signal and the received signal. However, if the first radio unit implements FDD the transmitted signal and the received signals occur over orthogonal spectral regions within the first frequency bandwidth (FBACKHAUL).

As described above, the control unit <NUM>-A also generates one or more control signals to cause the second radio unit <NUM>-A to: provide uplink radio access connectivity to one or more end-user nodes using the second frequency bandwidth (FEND-USER), provide downlink radio access connectivity to one or more end-user nodes using the second frequency bandwidth (FEND-USER), transmit backhaul information to another radio node using the second frequency bandwidth (FEND-USER), and/or receive backhaul information from another radio node using the second frequency bandwidth (FEND-USER).

When the second radio unit <NUM>-A is configured to receive backhaul information from another radio node, and/or provide uplink radio access connectivity to one or more end-user nodes, an incoming signal <NUM>, <NUM>-A in the second frequency bandwidth (FEND-USER) is intercepted by the antenna unit <NUM>. The antenna unit <NUM> then provides the incoming signal to the RF unit <NUM>. The RF unit <NUM> performs well-known RF processing on the incoming signal such as, but limited to, amplification, down-conversion, automatic gain control, filtering and/or any combination thereof. The processed signal is then provided to the modem <NUM> for baseband processing of the signal.

When the second radio unit <NUM>-A is configured to transmit backhaul information to one or more other radio nodes, and/or, provide downlink radio access connectivity to one or more end-user nodes, the modem <NUM> outputs one or more signals that are provided to the RF unit <NUM>. The RF unit <NUM> performs well-known RF operations on the input signals, such as, but not limited to, filtering, up-conversion, amplification, recombination and/or any combination thereof. Accordingly, the RF unit <NUM> may be implemented in hardware by one or more of a filter, up-converter, amplifier, and/or a multiplier. The RF unit <NUM> then provides the processed RF signal to the antenna unit <NUM> which transmits the signal <NUM>, <NUM>-A using the second frequency bandwidth (FEND-USER).

The frequency bandwidth of the received signals <NUM>, <NUM>-A and/or the transmitted signals <NUM>, <NUM>-A may have a frequency bandwidth that corresponds to the second frequency bandwidth (FEND-USER) or a portion thereof based on the specific frequency planning, duplexing mode and scheduling policy employed. For example, if the first radio unit implements TDD the totality of the second frequency bandwidth (FEND-USER) may be assigned or allocated to both the transmitted signals <NUM>, <NUM>-A and the received signals <NUM>, <NUM>-A. However, if the second radio unit implements FDD the transmitted signals <NUM>, <NUM>-A and the received signals <NUM>, <NUM>-A occur over orthogonal spectral regions within the second frequency bandwidth (FEND-USER).

In some cases, the antenna unit <NUM> may comprise a plurality of antenna elements (not shown) to support multiple-input-multiple-output (MIMO) communications. Each of the antenna elements may be adapted to be coupled to a tuneable circuit with variable phase and amplitude response. An antenna element may, for example, be an elementary waveguide radiator, a cluster of radiators, a parabolic antenna or any other suitable antenna element.

The modem <NUM> may comprise one or more functional modules for processing received signals or generating signals for transmission. The functional modules may include one or more of: a functional module for performing conventional baseband processing such as modulation/demodulation and coding/decoding; a functional module to perform MIMO processing tasks to leverage the spatial multiplexing and diversity gains that can be provided with multiple antenna elements <NUM>; a functional module to perform power adaption, bit loading and/or spatial mode selection; and a functional module to provide support for medium access control and radio resource management tasks.

The radio node <NUM>-A may also comprise an interface unit <NUM> that is configured to adapt information received by the second radio unit over the second frequency bandwidth (FEND-USER) to a suitable format (e.g. a suitable frame format) for transmission by the second radio unit over the second frequency bandwidth (FEND-USER) or for transmission by the first radio unit over the first frequency bandwidth (FBACKHAUL); and to adapt information received by the first radio unit over the first frequency bandwidth (FBACKHAUL) to a suitable format (e.g. a suitable frame format) for transmission by the second radio unit over the second frequency bandwidth (FEND-USER) or for transmission by the first radio unit over the first frequency bandwidth (FBACKHAUL). Specifically, the interface unit <NUM> may be configured to convert backhaul information to uplink/downlink radio access information and vice versa. The amount of information that is transmitted through each radio unit may be dictated by the control signals generated by the control unit <NUM>-A.

The radio node <NUM>-A may also comprise a synchronization unit <NUM> that is configured to synchronize the operation of the radio node (and in particular the control unit <NUM>-A) with the operation of one or more other radio nodes (and, in particular, the control units thereof). In some examples, the synchronization unit <NUM> may be configured to perform frequency and time synchronization tasks. For example, in some cases, the synchronization unit <NUM> may be configured to obtain synchronization information, such as signals emitted by Global Navigation Satellite System (GNSS) transmitters and use that to ensure that the radio node (and in particular the control unit) is operating in accordance with the synchronization information. In other cases, the synchronization unit may be alternatively, or additionally, configured to implement synchronization functionalities prescribed by the IEEE <NUM> Precision Time Protocol for enabling distributed network synchronization.

Claim 1:
A control unit (<NUM>-A, <NUM>-B) for controlling a radio node (<NUM>-A, <NUM>-B) comprising a first radio unit (<NUM>-A, <NUM>-B) and a second radio unit (<NUM>-A, <NUM>-B), the control unit (<NUM>-A, <NUM>-B) configured to:
generate and output one or more control signals to cause:
the first radio unit (<NUM>-A, <NUM>-B) to exchange a first portion of backhaul information with another radio node (<NUM>-B, <NUM>-A) over a first communication link (<NUM>, <NUM>) established using a first frequency bandwidth (FBACKHAUL); the second radio unit (<NUM>-A, <NUM>-B) to provide uplink (<NUM>-A, <NUM>-B) and downlink (<NUM>-A, <NUM>-B) radio access connectivity to one or more end-user nodes (<NUM>-A, <NUM>-B) using a second frequency bandwidth (FEND-USER), wherein the second frequency bandwidth (FEND-USER) being different from the first frequency bandwidth (FBACKHAUL) ; and
the second radio unit (<NUM>-A, <NUM>-B) to exchange a second portion of the backhaul information with the other radio node (<NUM>-B, <NUM>-A) over a second communication link (<NUM>, <NUM>),
the second communication link (<NUM>, <NUM>) being established using the second frequency bandwidth (FEND-USER);
characterized in that the control unit (<NUM>-A, <NUM>-B) is configured to allocate none of the second frequency bandwidth (FEND-USER) for use in establishing the second communication link (<NUM>, <NUM>) in response to determining that a quality of the first communication link (<NUM>, <NUM>) is greater than or equal to a minimum quality, and allocate a portion of the second frequency bandwidth (FEND-USER) for use in establishing the second communication link (<NUM>, <NUM>) in response to determining that the quality of the first communication link (<NUM>, <NUM>) is less than the minimum quality.