阅读说明：本技术 无线链路的容错传输 (Fault tolerant transmission of wireless links ) 是由 安东尼·雅明 马克·托马斯 乔治·迪安 于 2018-11-14 设计创作，主要内容包括：数据从包括第一发射机和第二发射机的第一无线站(1)传输到包括第一接收机和第二接收机的第二无线站(2)。在没有检测到无线电链路故障的情况下,使用第一无线电资源块的第一子集经由第一无线电链路从第一发射机向第一接收机传输第一数据,并且使用第一无线电资源块的第二子集经由第二无线电链路从第二发射机向第二接收机传输第二数据。监控第一无线电链路和第二无线电链路的故障。如果检测到第一无线电链路的故障,则使用第一无线电资源块的第一子集和第二子集的组合来操作第二无线电链路。如果检测到第二无线电链路的故障,则使用第一无线电资源块的第一子集和第二子集的组合来操作第一无线电链路。(Data is transmitted from a first wireless station (1) comprising a first transmitter and a second transmitter to a second wireless station (2) comprising a first receiver and a second receiver. In the case where no radio link failure is detected, first data is transmitted from a first transmitter to a first receiver via a first radio link using a first subset of the first radio resource blocks, and second data is transmitted from a second transmitter to a second receiver via a second radio link using a second subset of the first radio resource blocks. The first radio link and the second radio link are monitored for failure. If a failure of the first radio link is detected, the second radio link is operated using a combination of the first subset and the second subset of the first radio resource blocks. If a failure of the second radio link is detected, the first radio link is operated using a combination of the first subset and the second subset of the first radio resource blocks.)

1. A method of transmitting data from a first wireless station comprising a first transmitter and a second transmitter to a second wireless station comprising a first receiver and a second receiver, the method comprising:

transmitting, without detecting a radio link failure, first data from the first transmitter to the first receiver via a first radio link using a first subset of first radio resource blocks, and second data from the second transmitter to the second receiver via a second radio link using a second subset of the first radio resource blocks;

monitor the first radio link and the second radio link for a failure of the first radio link or the second radio link; and is

Operating the second radio link from the second transmitter to the second receiver using a combination of the first subset and the second subset of the first radio resource blocks if a failure of the first radio link is detected, and

operating the first radio link from the first transmitter to the first receiver using a combination of the first and second subsets of the first radio resource blocks if a failure of the second radio link is detected.

2. The method of claim 1, wherein the first subset of the first radio resource blocks comprises a first slot occupying a first frequency channel, and the second subset of the first radio resource blocks comprises a second slot occupying the first frequency channel.

3. The method of claim 1, wherein the first subset of the first radio resource blocks comprises a first frequency channel in a first slot, and the second subset of the first radio resource blocks comprises a second frequency channel in the first slot.

4. A method according to any preceding claim, wherein the first radio resource blocks occupy successive frequency allocations and successive time allocations within a recurring time slot.

5. The method of any preceding claim, wherein the first data and the second data comprise payload data.

6. The method of claim 5, comprising:

demultiplexing a payload data stream into a first data stream transmitted via the first radio link and a second data stream transmitted via the second radio link without detecting the radio link failure;

aggregating, at the second wireless station, data received via the first radio link with data received via the second radio link;

transmitting the payload data stream via the second radio link if a failure of the first radio link is detected; and is

Transmitting the payload data stream via the first radio link if a failure of the second radio link is detected.

7. A method according to claim 5 or claim 6, wherein the first subset of the first radio resource blocks has substantially the same capacity as the second subset of the first radio resource blocks.

8. The method of any of claims 1-3, wherein the first data comprises payload data and the second data comprises control data and does not comprise the payload data.

9. The method of claim 8, comprising:

switching the payload data stream for transmission via the first radio link without detecting a failure of the first radio link; and is

Switching the payload data stream for transmission via the second radio link if a failure of the first radio link is detected, and

switching the payload data flow for transmission via the first radio link if a failure of the second radio link is detected.

10. The method according to claim 8 or 9, wherein the capacity of the first subset of radio resource blocks is larger than the capacity of the second subset of radio resource blocks.

11. The method of claim 10, wherein a capacity of the first subset of the radio resource blocks is greater than 9 times a capacity of the second subset of the radio resource blocks.

12. The method according to any of the preceding claims, wherein the first and second subsets of radio resource blocks are radio resource blocks within a transmission slot of a TDD frame.

13. The method of claim 12, wherein the first and second wireless stations are part of a wireless network that further includes wireless stations that are frame synchronized according to TDD and TDMA protocols.

14. A first wireless station comprising a primary master radio and a secondary master radio, the first wireless station configured to transmit data from the first wireless station to a second wireless station comprising a primary slave radio and a secondary slave radio,

the first wireless station includes a controller configured to:

in the event that no radio link failure is detected, causing the primary master radio to transmit first data from the primary master radio to the primary slave radio via a first radio link using a first subset of first radio resource blocks, and causing the secondary master radio to transmit second data from the secondary master radio to the secondary slave radio via a second radio link using a second subset of the first radio resource blocks;

monitor the first radio link and the second radio link for a failure of the first radio link or the second radio link; and is

In accordance with the detection of the failure of the first radio link, cause the secondary primary radio to use a combination of the first and second subsets of the first radio resource blocks for the second radio link, and

in accordance with the detection of the failure of the second radio link, cause the primary master radio to use a combination of the first and second subsets of the first radio resource blocks for the first radio link.

15. The first wireless station of claim 14, wherein the controller is configured to cause the first wireless station to perform the method of any of claims 1-13,

wherein the primary master radio comprises a first transmitter, the secondary master radio comprises a second transmitter, the primary slave radio comprises a first receiver, and the secondary slave radio comprises a second receiver.

Technical Field

The present invention relates generally to fault tolerant transmission of wireless links and more particularly, but not exclusively, to a method of efficiently allocating wireless resources for primary and secondary radio links which provides redundancy to enable operation to continue in the event of failure of one of the radio links.

Background

It may be desirable to provide fault tolerant transmission for data transmitted over a radio link. For example, the radio link may take the form of a microwave link, which may have a range of several kilometers between antenna towers, as a point-to-point or point-to-multipoint broadband link between two wireless stations. The wireless link may connect the master wireless station to a slave wireless station controlled by the master wireless station. Wireless stations on the link transmit and receive according to predetermined time division duplex and time division duplex sequences, with the timing of transmissions from each wireless station determined relative to a common time reference. Typically, transmission occurs in designated time slots within a predetermined sequence of frames.

One known method of providing fault tolerant transmission is to multiplex data between two radio links and aggregate the data upon reception. If a failure is detected on one radio link, the data is directed to a good radio link. This effectively utilizes the equipment in the no fault condition, but provides reduced capacity in the fault condition. Another known method of providing fault tolerant transmission is to provide a so-called "hot standby" system. Two transmitters and two receivers are provided, which are typically arranged to use the same frequency and polarization. In the absence of a fault, one transmitter is active and transmits data, the other is silent and does not transmit data, and both receivers are active and receive a common signal from the active transmitter. Data is acquired from only one of the receivers. In case of a link failure, another receiver may be used if the receiver fails or another transmitter may be used if the transmitter fails. This maintains capacity in the failed state, but the use of the device is inefficient, and delays may occur in establishing the link and data may be interrupted when switching to another transmitter.

Aspects of the present invention reduce the limitations of prior art systems.

Disclosure of Invention

According to a first aspect of the present invention, there is provided a method of transmitting data from a first wireless station comprising a first transmitter and a second transmitter to a second wireless station comprising a first receiver and a second receiver, comprising:

in the event that no radio link failure is detected, transmitting first data from a first transmitter to a first receiver via a first radio link using a first subset of the first radio resource blocks, and transmitting second data from a second transmitter to a second receiver via a second radio link using a second subset of the first radio resource blocks;

monitoring the first radio link and the second radio link for a failure of the first radio link or the second radio link; and is

Operating a second radio link from a second transmitter to a second receiver using a combination of the first and second subsets of the first radio resource blocks if a failure of the first radio link is detected, and

if a failure of the second radio link is detected, a combination of the first and second subsets of the first radio resource blocks is used to operate the first radio link from the first transmitter to the first receiver.

This allows maintaining the data capacity in the failed state by reallocating the radio resources of the failed link to the good links and maintaining the operation of both links without failure to reduce the start-up time in the case of failure and to provide assurance that the system will operate correctly in the event of failure of one link.

In an embodiment of the invention, the first subset of the first radio resource blocks comprises first time slots occupying a first frequency channel and the second subset of the first radio resource blocks comprises second time slots occupying the first frequency channel.

This allows the capacity of the working radio link to be increased by increasing the length of the time slot used by the working radio link in the time allocated to both radio links when a failure is detected in the other radio link.

In an embodiment of the invention, the first subset of the first radio resource blocks comprises a first frequency channel in the first time slot and the second subset of the first radio resource blocks comprises a second frequency channel in the first time slot.

This allows the capacity of the working radio link to be increased by increasing the frequency bandwidth used by the working radio link within the bandwidth allocated to both radio links when a failure is detected in the other radio link.

In one embodiment of the invention, the first radio resource blocks occupy consecutive frequency allocations and consecutive time allocations within a recurring time slot.

This allows for efficient use of reallocated radio resources in fault conditions by extending the time slot and/or frequency bandwidth.

In an embodiment of the invention, the first data and the second data comprise payload data.

This allows the payload data to be used to maintain synchronisation of the two radio links in the absence of a fault condition.

In an embodiment of the invention, the method comprises:

in the event that no radio link failure is detected, demultiplexing the payload data stream into a first data stream transmitted via the first radio link and a second data stream transmitted via the second radio link, and aggregating data received via the first radio link with data received via the second radio link at the second wireless station; and is

Transmitting a payload data stream via a second radio link if a failure of the first radio link is detected; and is

The payload data stream is transmitted via the first radio link if a failure of the second radio link is detected.

This allows the payload data to be used to maintain synchronisation of the two radio links in a fault-free state.

In an embodiment of the invention, the first subset of the first radio resource blocks has substantially the same capacity as the second subset of the first radio resource blocks.

This allows for a convenient implementation.

In an embodiment of the invention, the first data comprises payload data, the second data comprises control data and no payload data.

This allows for a simple implementation by avoiding the need for data multiplexing and aggregation.

In an embodiment of the invention, the method comprises:

switching the payload data stream for transmission via the second radio link if a failure of the first radio link is detected, and

switching the payload data stream for transmission via the first radio link if a failure of the second radio link is detected.

This allows for a simple implementation by avoiding the need for data multiplexing and aggregation.

In an embodiment of the invention, the capacity of the first subset of radio resource blocks is larger than the capacity of the second subset of radio resource blocks.

This allows for increased data capacity while using data switches rather than multiplexers/demultiplexers without a failure condition.

In an embodiment of the invention, the capacity of the first subset of radio resource blocks is greater than 9 times the capacity of the second subset of radio resource blocks.

This allows an efficient implementation.

In an embodiment of the invention, the first and second subsets of radio resource blocks are radio resource blocks within a transmission slot of a TDD frame.

This allows an efficient implementation.

In one embodiment of the invention, the first and second wireless stations are part of a wireless network that also includes synchronized wireless stations according to TDD and TDMA protocols.

This allows the first and second wireless stations to be used in a wireless network with other wireless stations.

According to a second aspect of the present invention, there is provided a first wireless station comprising a primary master radio and a secondary master radio, the first wireless station being configured for transmitting data from the first wireless station to a second wireless station comprising a primary slave radio and a secondary slave radio,

the first wireless station includes a controller configured to:

in the event that no radio link failure is detected, causing the primary master radio to transmit first data from the primary master radio to the primary slave radio via the first radio link using a first subset of the first radio resource blocks, and causing the secondary master radio to transmit second data from the secondary master radio to the secondary slave radio via the second radio link using a second subset of the first radio resource blocks;

upon detection of the first radio link failure, causing the secondary primary radio to use a combination of the first and second subsets of the first radio resource blocks for the second radio link, and

in accordance with the detection of the second radio link failure, the primary master radio device is caused to use a combination of the first subset and the second subset of the first radio resource blocks for the first radio link.

Further features of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only.

Drawings

Fig. 1a is a schematic diagram showing the transmission of data from a first wireless station to a second wireless station without a fault condition, the data being multiplexed for transmission over a first radio link in a first time slot and over a second radio link in a second time slot;

FIG. 1b is a schematic diagram illustrating the system of FIG. 1a in a failure state of a first radio link, transmitting data over a second radio link in first and second time slots;

fig. 2a is a schematic diagram showing the transmission of data from a first wireless station to a second wireless station without a fault condition, switching the data for transmission over a first radio link in a first longer time slot and additional data, e.g., control data, over a second radio link in a second shorter time slot;

FIG. 2b is a schematic diagram showing the system of FIG. 2a in a failure state of a first radio link, the data being transmitted over a second radio link in first and second time slots;

fig. 3a is a schematic diagram showing the transmission of data from a first wireless station to a second wireless station without a fault condition, the data being multiplexed for transmission over a first radio link in a first longer time slot and over a second radio link in a second shorter time slot;

FIG. 3b is a schematic diagram showing the system of FIG. 3a in a failure state of a first radio link, the data being transmitted over a second radio link in first and second time slots;

fig. 4a is a schematic diagram showing the transmission of data from a first wireless station to a second wireless station without a fault condition, the data being multiplexed for transmission over a first radio link in a first frequency channel and over a second radio link in a second frequency channel, the first and second frequency channels being adjacent channels;

FIG. 4b is a schematic diagram showing the system of FIG. 4a in a failure state of a first radio link over which data is transmitted in an extended frequency channel occupying the bandwidth of the first and second frequency channels;

figure 5a shows a radio resource block comprising two slots;

figure 5b shows a radio resource block comprising two frequency channels;

FIG. 6 shows a series of time division duplex frames;

fig. 7a is a diagram showing data transmission between a first wireless station and a second wireless station in a non-failure state in a time division duplex system, multiplexing downlink data for transmission from the first wireless station to the second wireless station over a first radio link in a first downlink time slot and over a second radio link in a second downlink time slot, multiplexing uplink data for transmission from the second wireless station to the first wireless station over the first radio link in a first uplink time slot and over the second radio link in a second uplink time slot;

FIG. 7b is a schematic diagram showing the system of FIG. 7a in a failure state of a first radio link, the data being transmitted over a second radio link in first and second respective downlink and uplink time slots;

FIG. 8 shows a series of frames according to a time division duplex and time division multiple access system;

fig. 9a is a schematic diagram showing data transmission between a first wireless station and second and third wireless stations in a time division duplex system and time division multiple access without a fault condition;

fig. 9b is a schematic diagram showing the system of fig. 9a in a failure state of a first radio link between first and second wireless stations;

fig. 10 is a schematic diagram showing first and second wireless stations;

FIG. 11 is a flow chart illustrating a method according to an embodiment of the present invention; and

FIG. 12 is a flow chart illustrating a method according to an embodiment of the present invention.

Detailed Description

By way of example, embodiments of the present invention will now be described in the context of a point-to-point microwave broadband link that functions as a time division duplex system at a carrier frequency typically between 3GHz and 6 GHz. However, it will be appreciated that this is merely exemplary and that other embodiments may relate to other wireless systems and frequencies, and that embodiments are not limited to a particular operating frequency band or a particular standard and may relate to operating within a licensed or unlicensed frequency band. Typical applications include backhaul systems and microwave ethernet bridges for providing connectivity to small and large cellular infrastructures, for leased line replacement, and for providing fast deployment video, voice and data services for disaster recovery.

Fig. 1a and 1b show an embodiment of the invention. Fig. 1a shows the transmission of data from a first radio station 1 to a second radio station 2 in a non-faulty state. As shown in fig. 1a, the duration t is used in case no failure of the first radio link is detected₁Is transmitted from a first transmitter in the primary master radio 3 of the first wireless station 1 to a first receiver in the primary slave radio 5 of the second wireless station 2 via a first radio link. Furthermore, the duration t is used₂Is transmitted via a second radio link from a second transmitter in a secondary master radio 4 of the first wireless station 1 to a second receiver in a secondary slave radio 6 of the second wireless station 2.

The first radio link and the second radio link are monitored for a failure of the first radio link or the second radio link. The monitoring may be performed by, for example, a control processor of the first radio station and may be based on monitoring of the receiver synchronization, fed back as signalling data from the second radio station. A synchronization failure may result in the detection of a link failure. Alternatively or additionally, the detection of the link failure may be based on detection of a packet error rate or a bit error rate that is greater than an acceptable threshold. To detect a link failure, an error or fault condition may be required to persist for at least a predetermined period of time. Other methods of detecting link failure may be used, for example, monitoring the received signal power level and detecting a failure if the received signal power level is below a threshold level for a predetermined period of time.

As shown in fig. 1b, if a failure of the first radio link is detected, a combination of the first and second subsets of the first radio resource blocks is used for the second radio link, in which case by extending the duration of the time slots used by the second radio link to have a duration t₃To occupy the time allocated to the first and second links, 13. This allows data capacity to be maintained in the failed state, which provides assurance that the system will function correctly in the event of a failure of one link, and avoids the required start-up time to establish allowed links, as the first and second links have already been established and monitored. The assurance that the system will function correctly in case of failure of one link and the avoidance of required start-up time are obtained at a potential cost by selecting the link only between two alternative established links, namely a first link from a first transmitter to a first receiver and a second link from a second transmitter to a second receiver. A potential cost of this approach is that selection by this approach will not allow selection of a cross-coupled link between the first transmitter and the second receiver or between the second transmitter and the first receiver. However, if both the first and second links are detected as faulty, then cross-coupling links may be attempted as a candidate, but without the advantages of guaranteed performance and no setup time. Thus, the present approach generally provides advantages if a single link fails, but at the cost of potential disadvantages if both links fail.

As shown in FIG. 1a, a first subset of first radio resource blocks comprises occupying a first frequency channel f₁First time slot of9, the second subset of the first radio resource blocks comprises occupying the same first frequency channel f₁The second time slot 10. This allows the capacity of the working radio link to be increased by increasing the length of the time slot used by the working radio link in the time allocated to both radio links when a failure is detected in the other radio link.

In the embodiment shown in fig. 1a and 1b, the first data and the second data comprise payload data. In case no failure of the first radio link is detected, the incoming data (in this example the payload data stream) to the first wireless station 1 is demultiplexed by the data multiplexing/demultiplexing function 7 into a first data stream for transmission via the first radio link and a second data stream for transmission via the second radio link. Upon reception at the second wireless station 2, the data received at the second wireless station via the first radio link is aggregated with the data received via the second radio link in the data multiplexing/demultiplexing function 8. As shown in fig. 1b, upon detection of a failure of the first radio link, the payload data stream is transmitted via only the second radio link and the data is not multiplexed or aggregated. This allows the payload data to be used in the absence of a fault condition to maintain synchronisation of the two radio links so that no delay is required to cause the second link to be started in the fault condition, since both links are already running.

As shown in fig. 1a, the first subset of the first radio resource blocks, in this case the first time slots 9, has substantially the same capacity as the second subset of the first radio resource blocks, in this case the second time slots 10.

Fig. 2a and 2b show an embodiment wherein the first data comprises payload data, the second data comprises control data and no payload data. The second data is used to maintain second data link synchronization. As shown in fig. 2a, in case no failure of the first radio link is detected, the payload data stream is exchanged by the data switch 14 for transmission via the first radio link. Upon reception by the second wireless station 2, the data switch 15 selects data received via the first radio link. As shown in fig. 2b, upon detection of the failure of the first radio link, payload data streams are exchanged by the data switch 15 for transmission via the second radio link in the extended time slot 21. Upon reception by the second wireless station 2, the data switch 15 selects data received via the second radio link. This allows for a simple implementation by avoiding the need for data multiplexing and aggregation.

As shown in fig. 2a, a first subset of radio resource blocks (in this case the duration t)₄Has a ratio to a second subset of radio resource blocks (in this case a ratio t)₄Short duration t₅The second time slot 18) of the larger capacity. This allows for an increase in data capacity without failure conditions using a data switch instead of a multiplexer/demultiplexer, so that only one radio link is used for transmitting payload data. The capacity of the first subset of radio resource blocks may be greater than 9 times the capacity of the second subset of radio resource blocks. In the absence of a fault condition, the asymmetry increases the payload data capacity.

Fig. 3a and 3b show the case where the payload data is demultiplexed at the first wireless station in case the first time slot 22 of the first radio link is longer than the second time slot 23 of the second radio link in the absence of a failure state between the first and second radio links. This may simplify multiplexing and aggregation of certain types of data. The second time slot is extended to a longer time slot 26 when the first radio link failure is detected.

Fig. 4a and 4B show an embodiment of the invention in which the first subset of first radio resource blocks 28 comprises a bandwidth B in the first time slot₁A second subset 29 of the first radio resource blocks comprises a second frequency channel in the same first time slot (again in this example with a bandwidth B)₁) Although the bandwidths may be different from each other. When a failure is detected in the first radio link failure, the frequency bandwidth used by the second radio link increases within the bandwidth allocated to both radio links, as shown in fig. 4b, in which caseIncrease to 2B under the circumstances₁. As shown in fig. 4a and 4b, in one embodiment of the invention, the first radio resource block occupies a continuous frequency allocation within the time slots 27, 30. This allows for efficient utilization of the reallocated radio resources in the failure state by extending the frequency bandwidth of the second radio link. In radios with selectable bandwidth, the expansion of bandwidth can be achieved directly. The expansion need not be limited to a double expansion; any expansion factor may be used as long as the expanded bandwidth is within the allocated range of the first and second links.

Fig. 1a, 1b, 2a, 2b, 3a and 3b show that the first radio resource block may occupy consecutive time allocations in the form of consecutive time slots. This does not exclude that a guard time (guard time) is included between the first and second time slots.

Fig. 5a shows a first radio resource block 32 in an embodiment, wherein the first radio resource block 32 comprises two time slots 33, 34.

Fig. 5b shows a first radio resource block 35 in an embodiment, wherein the first radio resource block 35 comprises two frequency channels 36, 37.

Fig. 6 shows a series of Time Division Duplex (TDD) frames including a downlink frame D L for transmission from the first wireless station 1 to the second wireless station 2 and an uplink frame U L for transmission from the second wireless station 2 to the first wireless station 1 as shown in fig. 6, the first radio resource block of fig. 5a may be transmitted in a recurring downlink slot D L, which in this example are recurring slots within the TDD frame as the first and second slots 33, 34, or a radio resource block comprising two frequency channels as shown in fig. 5b may be transmitted in a downlink slot.

Fig. 7a shows bidirectional data transmission between a first wireless station 1 and a second wireless station 2 in a TDD system in a no fault state, multiplexing downlink data for transmission from the first wireless station 1 to the second wireless station 2 over a first radio link in a first downlink time slot 38 corresponding to time slot 33 in fig. 6 and from the first wireless station 1 to the second wireless station 2 over a second radio link in a second downlink time slot 40 corresponding to time slot 34 in fig. 6, and multiplexing uplink data for transmission from the second wireless station to the first wireless station over the first radio link in a first uplink time slot 39 and from the second wireless station to the first wireless station over the second radio link in a second uplink time slot 41.

Fig. 7b shows the system of fig. 7a in a first radio link failure state, with the data being transmitted over the second radio link in extended time slots 42, 43 that occupy time allocated to the first and second respective downlink and uplink time slots in the absence of a failure.

In one embodiment of the invention, the first and second wireless stations are part of a wireless network that includes other wireless stations synchronized according to TDD and TDMA protocols. This allows the first and second wireless stations to be used in a wireless network with other wireless stations.

Fig. 8 shows a series of frames according to time division duplex and time division multiple access protocols.

Time slots 44 and 45 are used for downlink transmissions from the primary and secondary primary radios of the first or primary wireless station, respectively, to the primary and secondary radios of the second wireless station, which may be the first secondary station. Time slots 46 and 47 are used for downlink transmissions from the primary and secondary primary radios of the first or primary wireless station to the primary and secondary radios of a third wireless station, which may be a second secondary station, respectively. Time slots 48 and 49 are used for uplink transmissions from the primary and secondary radios of the second wireless station (which may be the first secondary station) to the primary and secondary primary radios of the first or primary wireless station, respectively. Time slots 50 and 51 are used for uplink transmissions from the primary and secondary radios of the third wireless station (which may be a second secondary station) to the primary and secondary primary radios of the first or primary wireless station, respectively. Although only two secondary stations are shown, this is for illustration only and more than two secondary stations may be used, each allocated downlink and uplink time slots within a TDD/TDMA frame.

Fig. 9a is a diagram showing data transmission in the time slot of fig. 8 in a time division duplex system and time division multiple access between the first wireless station 1 and the second wireless station 2a and the third wireless station 2b in a no failure state.

Fig. 9b is a schematic diagram illustrating the system of fig. 9a in a failure state of a first primary radio link between first and second wireless stations. It can be seen that the time slots 45 and 49 used by the secondary radios of the primary station 1 and the first secondary station 2a are spread in time to include the time slots 44 and 48 previously allocated to the failed first link between the primary radios. The longer time slots are shown as time slots 52 and 53. In this example, the time slot allocated in the link between the master station 1 and the second slave station 2b is not affected by the first link failure. This is because in this case the failure is caused by a problem in the first slave station 2a and does not affect any link to the second slave station 2 b. If the failure of the first link is due to a problem in the master station 1, both the link from the primary master radio 3 to the primary slave radio 5a of the first slave station 2a and the link from the primary master radio 3 to the primary slave radio 5b of the second slave station 2b will be affected. In this case, the time slots 47 and 51 for communication between the secondary master radio 4 and the secondary slave radio 6b will be extended to occupy the time previously allocated to the time slots 46 and 50.

Similar processing will occur if a failure is detected in the link between the secondary radios, the time slots used by the secondary radios being allocated to the primary radio. The names of "primary" and "secondary" radios may be arbitrary.

Fig. 10 shows in schematic form a first wireless station 1 and a second wireless station 2. A third radio station acting as a second secondary station in a TDMA scheme may also have the same block diagram as shown for the first and second radio stations. Considering the first wireless station 1, the data link 56 is typically connected to the first wireless station 1, typically a fiber optic connection, which may carry, for example, ethernet traffic. The data stream is processed in a data processing circuit element 54 under the control of a controller circuit element 55, which in some embodiments, the data processing circuit element 54 may be a multiplexer/demultiplexer circuit element that typically splits the data stream into two streams prior to transmission and aggregates the two data streams upon reception. If a fault condition is detected, multiplexing and aggregation may be disabled and data routed via the second radio link. In another embodiment, the data processing circuit element 54 may be a data switch that routes data flows via the first or second wireless links under the control of the controller 55. The data processing circuit elements 54 may be implemented using well-known techniques including digital signal processing integrated circuits, programmable gate arrays, dedicated hardware.

The controller 55, which may also be referred to as a processor, may include program code stored in memory that is configured to cause the controller to perform methods of embodiments of the present invention. The processor may include one or more digital signal processors and/or programmable logic arrays.

The primary main radio 3 and the secondary main radio 4 are each connected to and controlled by the controller 55 and each include conventional baseband signal processing circuit elements and conventional up-and down-conversion circuit elements, including filtering, amplifying and mixing elements that are common in radio transceivers. Each radio may be connected to a respective antenna, as shown, or both radios may be connected to the same antenna.

The second wireless station 2 may have the same structure as the first wireless station 1. The names of "master radio" and "slave radio" may be arbitrary, equivalent to "first radio" and "second radio". Typically, the master radio sets the time of the slave radio, but this may not be the case in all embodiments, and the two radios may be equivalent to each other. A radio typically includes a transmitter and a receiver.

The names of "primary radio" and "secondary radio" may also be arbitrary, equivalent to "first radio" and "second radio". In particular, in the embodiments of fig. 1a, 1b, 3a, 3b, 4a, 4b, 7a and 7b, any radio may be a primary radio in terms of the method of operation; the primary radio is the radio whose failure is detected.

The data processing circuit elements 57 of the second radio station 2 are typically identical to the data processing circuit elements of the first radio station 1.

The slave controller 58 of the second wireless station 2 may generally have the same structure as the controller 55 of the first wireless station and may or may not have the same program code. The second wireless station typically has a data link connection 59 similar to the first wireless station.

Fig. 11 is a flow chart illustrating a method according to an embodiment of the invention according to steps S11.1, S11.2 and S11.3, and fig. 12 is a flow chart illustrating a method according to an embodiment of the invention according to steps S12.1, S12.2 and S12.3.

Thus, various embodiments of the present invention have been described, including payload data switches such as shown in fig. 2A and 2B or payload data multiplexers such as shown in fig. 1A and 1B. In each case, this allows data capacity to be maintained in the failed state by reallocating the radio resources of the failed link to good links, and maintaining operation of both links without failure to reduce start-up time in the event of failure, and to provide assurance that the system will operate correctly in the event of failure of one link. In the case of using a payload data switch, a link is maintained by signaling data that does not include payload data without detecting a failure. In the case of using a payload data multiplexer, both links are maintained with payload data without detecting a failure. In some cases this may allow to keep the data flow with less impact on e.g. packet delay than in the case of a data switch, but at the cost of a higher complexity of the multiplexer.

The implementation using a data switch may be referred to as a 1+1 solution. This uses a data switch to provide active payload data to only one link, while the other link is inactive with respect to the payload data, maintained by signaling data. Preferably, links that are inactive with respect to payload data are configured to consume a small fraction, e.g., 10%, of the total time or frequency resources. Bridged payload traffic is typically carried only by the active link. When one link (e.g., the primary link) fails, the remaining link (in this case the secondary link) becomes active in terms of payload data and extends to using all resources.

The implementation using a multiplexer may be referred to as a 2+0 solution. This uses a multiplexer to provide two links carrying payload data without failure, sharing time or frequency resources. Payload traffic is demultiplexed and multiplexed so both links contribute to the overall capacity. When one link fails, traffic will be routed through the remaining links, which will expand to use all resources.

The 1+1 solution is generally simpler to implement and does not require potentially complex multiplexing functions. After a failure, the capacity of the 1+1 solution may increase. The 2+0 solution typically provides a slightly higher capacity in normal operation, since all resource blocks are used for transmitting data.

The 1+1 solution monitors the operation of devices that are inactive with respect to payload data and provides assurance that they can take over in the event of a failure. Conventional systems do not fully guarantee that inactive radios will operate properly after a protection switch. Embodiments of the present invention provide this assurance by maintaining and monitoring both links. However, this may be at the cost of a transmitter that would not normally allow the use of one link and a receiver of another link to establish a link, as may be the case in a conventional hot standby system.

The 1+1 solution allows for the establishment of inactive links in advance, so protection switching involves only an extension of the time or frequency dimension. This allows the use of air interface methods which inherently require time to establish a link without excessive downtime when the active link fails, for example OFDM (orthogonal frequency division multiplexing). This air interface approach may be particularly suitable for non-ideal wireless paths, e.g., non-line-of-sight.

The 2+0 solution preserves the total capacity in the event of a link failure, whereas the capacity of conventional systems typically drops to 50%.

The above embodiments are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.