Terminal having a variable duplex capability

A cellular telecommunications terminal having a full-duplex mode of operation and a half-duplex mode of operation, including a first cellular transmitter and a first cellular receiver operable, when the terminal is in the full-duplex mode, to transmit and receive at the same time and operable, when the terminal is in the half-duplex mode, to transmit and receive at different times and not at the same time; and a switching control for changing the mode of operation of the terminal while operating in the full-duplex mode from the full-duplex mode to the half-duplex mode.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a cellular telecommunications terminal. In particular, they relate to terminals having different duplex capabilities.

BACKGROUND TO THE INVENTION

It is known to have cellular telecommunications terminals that operate in a half-duplex mode i.e. they do not transmit and receive at the same time. An example of such a terminal is a GSM mobile telephone and some GPRS mobile telephones.

It is known to have cellular telecommunications terminals that operate in a full-duplex mode i.e. they transmit and receive at the same time. An example of such a terminal is a high-end GPRS mobile telephone and a WCDMA mobile telephone.

A dual mode telephone may therefore change its duplex capability by switching from a GSM mode of operation to a WCDMA mode of operation. The RF circuitry and antennas used for respectively operating in the GSM mode and WCDMA mode will typically be different and separate.

A key component of a full-duplex terminal is a duplexer which connects the transmitter and receiver to the antenna and prevents the symbols transmitted by the transmitter interfering with the symbols received by the receiver. Duplexers are expensive, consume power and have a large volume. It would therefore be desirable to reduce the use of duplexers or to use cheaper, less power hungry and smaller duplexers.

Currently duplexers are designed to provide enough isolation between the receiver and transmitter when the transmitter is operating at maximum power. If this constraint were relaxed, it may be possible to use cheaper, less power hungry and smaller duplexers.

There is a current trend towards the use of multiple antennas within a terminal. These antennas each have their own associated channels or may diversify a channel. However, the addition of multiple antennas typically also requires the use of multiple duplexers to isolate every receiver branch from every transmitter branch. It would be desirable to provide for the use of multiple antennas without the use of a duplexer at each antenna.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment of the invention there is provided a cellular telecommunications terminal having a full-duplex mode of operation and a half-duplex mode of operation, comprising: a first cellular transmitter and a first cellular receiver operable, when the terminal is in the full-duplex mode, to transmit and receive at the same time and operable, when the terminal is in the half-duplex mode, to transmit and receive at different times and not at the same time; and a switching control for changing the mode of operation of the terminal while operating in the full-duplex mode from the full-duplex mode to the half-duplex mode.

The switching control may also change the mode of operation of the terminal while operating in the half-duplex mode from the half-duplex mode to the full-duplex mode.

The terminal may consequently either operate at its full capability i.e. in full-duplex mode or at a reduced capability i.e. half-duplex mode. The switch between modes may, for example, occur when the duplexer separating the first transmitter and the first receiver reaches its isolation limit. This may, for example, be detected by detecting the self-interference at the first receiver from the first transmitter or by detecting the power of transmission from the first transmitter.

The ability of the terminal to operate at different duplex capabilities allows the network to allocate resources according to those capabilities. The terminal may inform the network of its current duplex capabilities

The network further offers any terminal, with any defined duplex capability, resources to efficiently operate in the network. The terminal may, but need not, be able to switch its duplex capability, but it shall be able to uniquely signal its duplex capability.

According to another embodiment of the invention there is provided a cellular telecommunications terminal having a full-duplex mode of operation and a half-duplex mode of operation, comprising: a plurality of cellular transmitters and receivers; and a controller for controlling at least one of the transmitters to transmit a capability message indicating the duplex capability of each of multiple antennas.

The terminal may have a fixed duplex capability or it may have a variable duplex capability. If the duplex capability is variable, then the capability message may indicate the current capability of the terminal.

According to another embodiment of the invention there is provided a cellular telecommunications network element comprising: a controller arranged to use a received capability message indicating the current duplex capability of each of multiple antennas, of a terminal to allocate resources in the network.

According to another embodiment of the invention there is provided a cellular telecommunications terminal having a full-capability mode of operation in which at least one antenna is capable of full-duplex operation and a reduced-capability mode of operation in which the at least one antenna is capable of half-duplex operation, the terminal comprising: a plurality of cellular transmitters and receivers; and a controller for controlling at least one of the transmitters to transmit a capability message indicating the reduced-capability mode of operation.

According to another embodiment of the invention there is provided a cellular telecommunications network element comprising: a controller arranged to use a received capability message indicating the reduced-capability mode of operation to allocate resources in the network.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1illustrates a cellular telecommunications system1including a cellular telecommunications network2and a plurality of cellular telecommunication terminals10A,10B,10C. Each cell4of the network is served by a base station6and the base stations are controlled by core network elements8.

One of the cellular telecommunications terminals may be half-duplex capable. The half-duplex capable terminal comprises a first cellular transmitter for transmitting in a first transmission frequency band, a first cellular receiver for receiving in a first reception frequency band, different to the first transmission frequency band. The half-duplex terminal does not include any duplexer.

At least one of the cellular telecommunications terminals10is full-duplex capable. The full-duplex capable terminal10is schematically illustrated inFIG. 2. It comprises a first cellular transmitter21for transmitting in a first transmission frequency band, a first cellular receiver31for receiving in a first reception frequency band, different to the first transmission frequency band, and a duplexer41joining the first cellular transmitter21and first cellular receiver31to a first antenna51. In other embodiments, the duplexer may, instead of being placed where the Rx path and Tx path join the antenna, it may be placed in either the Rx path or the Tx path.

The terminal10has a full-duplex mode of operation in which the first cellular transmitter21transmits symbols from the first antenna51and the first cellular receiver31simultaneously receives symbols via the first antenna51. The isolation provided by the duplexer41prevents the transmitted symbols interfering with the received symbols i.e. prevents self-interference.

The terminal10has a half-duplex mode of operation in which transmission and reception occurs at different times and not at the same time. The first cellular transmitter21transmits symbols from the first antenna51at first times and the first cellular receiver31receives symbols via the first antenna51at second times, different to the first times.

The terminal10additionally comprises a controller12. The controller12provides a switching control14and signalling control16.

Switching control14changes the mode of operation of the terminal10. When the terminal is operating in the full-duplex mode, the switching control14can change the operation mode from the full-duplex mode to the half-duplex mode. When the terminal10is operating in the half-duplex mode, the switching control14can change the operational mode from the half-duplex mode to the full-duplex mode.

The trigger for the switching control14may be provided by any one of a number of different means.

In one embodiment, a signal received from the network2via receiver31functions as the trigger.

In another embodiment, the trigger is the connection of the device10to another device such as a docking station with external antennas or improved power supply etc.

In another embodiment, self-interference detection performed at the terminal10functions as the trigger. The interference in the symbols received at the first cellular receiver is detected. The received signal strength indicator (RSSI), the received signal-to-interference ratio (SIR), the received interference power, the bit error rate (BER), the frame error rate (FER) etc may be used as a measure of interference. A measure of self interference may, for example, be obtained by measuring interference power when the transmitter is on and measuring interference power when the transmitter is off. The change in operational mode to half-duplex mode is triggered when the detected (self) interference exceeds a first predetermined interference threshold. The change in operational mode back to full-duplex mode is triggered when the detected (self) interference falls beneath a second predetermined interference threshold. The first and second thresholds may be different (bi-stability) or the same. Crossing a threshold may involve timing constraints to avoid too frequent change of modes.

In another embodiment, the power output of the cellular transmitter21functions as the trigger. The change in operational mode to half-duplex mode is triggered when the power output exceeds a first predetermined power threshold. The change in operational mode back to full-duplex mode is triggered when the power output falls beneath a second predetermined power threshold, which is typically the same as the first predetermined threshold but may be different. The power threshold may be dependent upon the characteristics of the duplexer. In one example, the predetermined power threshold is chosen so that the isolation provided by the duplexer41between the first cellular transmitter21and first cellular receiver31is adequate while the power output of the first transmitter21does not exceed the predetermined threshold and is inadequate when the power output of the first transmitter21exceeds the predetermined threshold.

In a preferred embodiment, the switching control14is not immediately responsive to a trigger but first exchanges messages with the network2before making the change in operational mode as illustrated inFIG. 3.

In response to a trigger, the signalling control16of the controller12controls the first transmitter21to send a request message71to the network2. The request message71identifies the new operational mode and may be sent as a capability information message.

If the first receiver31of the terminal10receives a reply message72from the network2, the switching control14changes73the operational mode of the terminal. The switch may optionally be delayed until further confirmation of the switch is received from the network2.

The messages71,72may be discrete messages or may be included as Information elements in some other messages.

The network2changes the resource allocation74to take account of the change in mode of the terminal10. For example, if the terminal10were in full-duplex mode there is no constraint upon when the terminal10is expected to transmit to the network2and is transmitted to by the network2. However, if the mode of the terminal10is changed to half-duplex, then transmissions to the terminal and transmissions from the terminal are constrained so that they do not coincide. The constraint is such that enough guard time is left between transmission and reception at the terminal10. Network2also has to reserve proper measurement intervals for terminal10to measure carriers on other frequencies, carriers on other frequency bands or carriers of other systems, so that the measurement intervals do not coincide with terminal transmissions to the network2nor transmissions by the network2to terminal10.

A full-duplex capable, multi-antenna terminal10′ is schematically illustrated inFIG. 4. It comprises the same components as described with reference toFIG. 2but additionally comprises a second cellular transmitter22, a second cellular receiver32and a switch element51joining the second cellular transmitter22and the second cellular receiver32to a second antenna52. The first and second transmitters operate on the same carrier frequency. The first and second receivers operate on the same carrier frequency. The carrier frequency of the transmitters is separate from the carrier frequency of the receivers. In some examples, the carrier frequency of the transmitters may be the same as the carrier frequency of the receivers, if proper constraints are respected for transmission and reception. In some examples, the first and second transmitters may operate on separate carrier frequencies or on carriers on separate frequency bands. Respectively, the first and second receiver may operate on separate carrier frequencies or on carriers on separate frequency bands.

The terminal10′ may only use one of its first and second transmitters and operate in a single input to uplink (SI-u) mode. The SI-u mode may be either a Single Input Single Output (SISO) mode, if the base station has a single receiver antenna or a Single Input Multiple Output (SIMO) mode, if the base station has more than one receiver antenna.

The terminal10′ may use both of its first and second transmitters and operate in a multiple input to uplink (MI-u) mode, The MI-u mode may be either a Multiple Input Single Output (MISO) mode, if the base station has a single receiver antenna or a Multiple Input Multiple Output (MIMO) mode, if the base station has more than one receiver antenna.

The terminal10′ may use one of its first and second receivers and operate in a single output from downlink (SO-d) mode. The SO-d mode may be either a SISO mode, if the base station has a single transmitter antenna or a MISO mode, if the base station has more than one transmit antennas.

The terminal10′ may use both of its first and second receivers and operate in a multiple output from downlink (MO-d) mode. The MO-d mode may be either a SIMO mode if the base station has a single transmitter antenna or a MIMO mode if the base station has more than one transmitter antenna.

The terminal10′ may operate as a single input uplink (SI-u) terminal by using only one of the transmitters21,22and as a single output downlink (SO-u) terminal by using only one of the receivers31,32. For example, if only the first transmitter21and first receiver31are used, then the terminal10′ may operate as either a full-duplex or half-duplex SISO terminal. If only the second transmitter22and the second receiver32are used, then the terminal10′ may operate as only a half-duplex SISO terminal.

The terminal10′ may operate as a multiple input single output (MISO) terminal by using both of the transmitters21,22(MI-u) and only one of the receivers31,32(SO-d). If the receiver used is the first receiver31, then the terminal10′ may operate as either a full-duplex or half-duplex (MISO) terminal10′. If the receiver used is the second receiver32, then the terminal10′ may operate as only a half duplex (MISO) terminal10′.

The terminal10′ may operate as a single input multiple output (SIMO) terminal by using one of the transmitters21,22(SI-u) and both of the receivers31,32(MO-d). If the transmitter used is the first transmitter21, then the terminal10′ may operate as either a full-duplex or half duplex (SIMO) terminal10′. If the transmitter used is the second transmitter22, then the terminal10′ may operate as only a half duplex (SIMO) terminal10′.

The terminal10′ may operate as a multiple input multiple output (MIMO) terminal by using both of the transmitters21,22(Ml-u) and both of the receivers31,32(MO-d). The terminal10′ may operate as only a half duplex MIMO terminal. If the switch61were replaced by a duplexer, terminal10′ may operate as a full-duplex MIMO terminal instead. If the duplexer41were originally replaced by a switch, terminal10′ may operate as only a half duplex terminal.

It will therefore be appreciated that the use of a switch element61instead of a duplexer41between the second transmitter22and the second receiver32, constrains some of the multi-antenna modes of the terminal10′ to half-duplex modes, whereas if a duplexer were used there would be an option of using either half-duplex or full-duplex modes. However, the reduction in the number of duplexers has significant advantages. Duplexers are expensive, consume power and occupy a large volume. These disadvantages become particularly problematic in multi-antenna terminals. Consequently the terminal10′ may be cheaper, smaller and more efficient than conventional multi-antenna terminals that use only duplexers.

The capability of the terminal10′ namely that only half-duplex is available for some combinations of the SI-u and MI-u modes with the SO-d and MO-d modes needs to be communicated to the network so that it can be taken into account in network resource allocation.

The signalling control16of the controller12controls the first transmitter21to send a message71to the network2. The message indicates duplex capability for each mode combination (SISO, SIMO, MISO, MIMO). The message may for example, indicate for each antenna of the terminal10′, whether an antenna is associated with a transmitter and receiver that are full-duplex capable or a transmitter and receiver that are not full-duplex capable. The message may be extended to indicate whether an antenna is associated with a transmitter only or a receiver only. The message71may be a discrete message or may be included as Information elements in some other message.

The terminal10′ may switch between full-duplex mode and half-duplex mode on a transition from using a single antenna to using multiple antennas or on any transition between multi-antenna configurations from SISO to SIMO, MISO or MIMO, from SIMO to SISO, MISO or MIMO, from MISO to SISO, SIMO or MIMO or from MIMO to SISO, SIMO or MISO.

Even when the terminal is capable of operating at full-duplex e.g. during MIMO modes (SISO, SIMO, MISO, MIMO), the terminal10may instead operate with reduced capabilities e.g. half-duplex within its set of full capabilities. A decision to operate with reduced capabilities may be made by the terminal10′ or the network. If it is made by the terminal, it needs to be communicated to the network. A convenient way of communicating is to send a new message71to the network2that identifies the reduced capabilities of the terminal10′ e.g. half-duplex at SISO, half-duplex at SIMO, half-duplex at MISO or half-duplex at MIMO.

The terminal10′ is able to switch between full-capabilities (e.g. full-duplex mode) and reduced capabilities (e.g. half-duplex mode). Switching control14changes the operational capabilities of the terminal10′. When the terminal10′ is operating in the full-duplex mode, the switching control14can change the operational mode from the full-duplex mode to the half-duplex mode. When the terminal10is operating in the half-duplex mode, the switching control14can change the operational mode from the half-duplex mode to the full-duplex mode (if possible).

The trigger for the switching control14may be provided by any one of a number of different means.

In one embodiment, a signal received from the network2via the transmitter21,22functions as the trigger.

In another embodiment, the trigger is the connection of the device10to another device such as a docking station with external antennas or improved power supply etc.

In another embodiment, self-interference detection performed at the terminal10functions as the trigger. While one receiver31,32is used to receive symbols the other receiver32,31is used to measure interference. A measure of self interference may be obtained by measuring interference when the transmitter is on and measuring interference when the transmitter is off. The change in operational mode to half-duplex mode is triggered when the detected (self) interference exceeds a first predetermined interference threshold. The change in operational mode back to full-duplex mode is triggered when the detected (self) interference falls beneath a second predetermined interference threshold. The first and second thresholds may be different (bi-stability) or the same. Crossing a threshold may involve timing constraints to avoid too frequent change of modes.

In another embodiment, the power output of the cellular transmitter21functions as the trigger. The change in operational mode to half-duplex mode is triggered when the power output exceeds a first predetermined power threshold. The change in operational mode back to full-duplex mode is triggered when the power output falls beneath a second predetermined power threshold, which is typically the same as the first predetermined threshold but may be different. Crossing a threshold may involve timing constraints to avoid too frequent change of modes. The power threshold may be dependent upon the characteristics of the duplexer41.

The use of the power output or self-interference as the trigger is useful for a reduced full-duplex capability implementation. In this implementation, the device is capable of operating in full-duplex mode unless one of the transmit power or self-interference exceeds their respective predetermined thresholds. The predetermined power threshold is chosen so that the isolation provided by the duplexer41between the first cellular transmitter21and first cellular receiver31is adequate while the power output of the first transmitter21does not exceed the predetermined threshold and is inadequate when the power output of the first transmitter21exceeds the predetermined threshold.

In a full-duplex implementation, the duplexer is capable of operating across the whole power and signal-to-noise ratio range of values.

It should be appreciated that in the foregoing, the full-duplex and half-duplex modes of operation are different modes of the same mobile telephone mode. That is the same FDD communication protocol is used in the full-duplex and half-duplex modes of operation.