WO2013128228A1 - Method and system for instructing a communication unit to perform a predefined processing - Google Patents

Abstract

Causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, comprises: obtaining first information representative of an instant at which a timing reference request message is transmitted by the first communication unit, according to the first clock reference; obtaining second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference; obtaining third information representative of an instant at which a processing request message is transmitted or has to be transmitted by the first communication unit, according to the first clock reference; and determining fourth information representative of an instant at which said predefined process has to be performed by said second communication unit according to said second clock reference, said fourth information being determined on the basis of the obtained first, second and third information.

Description

Method and system for instructing a communication unit to perform a

predefined processing

The present invention generally relates to causing a first communication unit to instruct a second communication unit to perform a predefined processing at a predetermined instant, whereas the first and second communication units have different clock references.

Such a situation typically occurs, among others, when a baseband integrated circuit is connected to a radio frequency integrated circuit in a mobile station or user equipment. Indeed, as radio-frequency integrated circuits incorporate analogue processing, changing their internal design may generate interferences with other onboard components and may generate electromagnetic loops. Such designs are then tough to tune in order to remove such interferences or electromagnetic loops, which involves long development cycles compared to digital processing circuits. Therefore, the radio frequency processing is generally located in a dedicated chip driven by its own clock reference and the baseband processing is located in another chip driven by a distinct clock reference. It can be noticed that the chip including the radio frequency processing may comprise part of the baseband processing. It can further be noticed that a same system clock may be input to the chip including the radiofrequency processing and to the chip including the baseband processing, but that said chips use distinct Phase-Lock Loops (PLL) to drive at least part of their internal processing, said distinct PLLs thus involving the chips being operating in different clock domains. The chip incorporating the baseband processing may further comprise application processing.

The first communication unit, such as the baseband integrated circuit, needs to control time instants at which some predefined processing are initiated by the second communication unit, such as the radio frequency integrated circuit. Such predefined processing is for instance a sampling process, or gain setting. To achieve this, it is known in the art that the first communication unit and the second communication unit communicate together via some inter-chip digital link conveying messages, and that the first communication unit transmits time accurate strobe messages over this interchip digital link. However, the time accuracy of those time accurate strobe messages is not good enough in some cases, such as for Observed Time Difference of Arrival (OTDoA) or for resuming transmission after a gap without causing a false detection of transmission timing adjustment. This time inaccuracy is due to the distinct clock references, or domains, used in the first and second communication unit. Indeed, whereas an interrupt in a computer system needs typically to be handled within a margin of few tens of microseconds, the aforementioned processes need to be handled within a margin of few nanoseconds. It means that every clock cycle may count.

To solve this issue, one can use a dedicated hardware line to transmit the time accurate strobe from the first communication unit to the second communication unit. This however involves an extra-cost in terms of hardware resources.

It is desirable to overcome the aforementioned problems.

In particular, it is desirable to provide a solution that allows improving the relative timing error between two events. Indeed, the aforementioned processes are related to relative timing between two events, and the corresponding absolute timing accuracy requirement is much more relaxed.

It is furthermore desirable to provide such a solution that limits the impact on the design of a radio -frequency integrated circuit used in combination with a baseband in a mobile station or user equipment of a cellular telecommunications network.

It is furthermore desirable to provide a cost-effective solution to the aforementioned problems. To that end, the present invention concerns a method for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference. The method comprises: obtaining first information representative of an instant at which a timing reference request message is transmitted by the first communication unit, according to the first clock reference; obtaining second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference; obtaining third information representative of an instant at which a processing request message is transmitted or has to be transmitted by the first communication unit, according to the first clock reference; and determining fourth information representative of an instant at which said predefined process has to be performed by said second communication unit according to said second clock reference, said fourth information being determined on the basis of the obtained first, second and third information.

Thus, thanks to the aforementioned steps related to the processing of the timing reference request message, the accuracy of the timing for performing the predefined process by the second communication unit is improved, whereas the first and second communication units belong to distinct clock domains.

The present invention also concerns a system for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, characterized in that said system comprises: means for obtaining first information representative of an instant at which a timing reference request message is transmitted by the first communication unit, according to the first clock reference; means for obtaining second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference; means for obtaining third information representative of an instant at which a processing request message is transmitted or has to be transmitted by the first communication unit, according to the first clock reference; and means for determining fourth information representative of an instant at which said predefined process has to be performed by said second communication unit according to said second clock reference, said fourth information being determined on the basis of the obtained first, second and third information. The present invention also concerns a system for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, wherein said system comprises circuitry causing the system to perform: obtaining first information representative of an instant at which a timing reference request message is transmitted by the first communication unit, according to the first clock reference; obtaining second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference; obtaining third information representative of an instant at which a processing request message is transmitted or has to be transmitted by the first communication unit, according to the first clock reference; and determining fourth information representative of an instant at which said predefined process has to be performed by said second communication unit according to said second clock reference, said fourth information being determined on the basis of the obtained first, second and third information.

The term system as used above means either a device, a plurality of devices cooperating to implement the aforementioned means or causing the implementation of the aforementioned means, a chip or chipset, or a plurality of chips or chipsets cooperating to implement the aforementioned means or causing the implementation of the aforementioned means.

The present invention also concerns a computer program that can be downloaded from a communication network and/or stored on a medium that can be read by a computer or processing device. This computer program comprises instructions for causing implementation of the aforementioned method, when said program is run by a processor.

The present invention also concerns information storage means, storing a computer program comprising a set of instructions causing implementation of the aforementioned method, when the stored information is read from said information storage means and run by a processor.

Since the features and advantages related to the system and to the computer program are identical to those already mentioned with regard to the corresponding aforementioned method, they are not repeated here. The characteristics of the invention will emerge more clearly from a reading of the following description of an example of embodiment, said description being produced with reference to the accompanying drawings, among which:

Fig. 1 schematically represents a communication device in which the present invention may be implemented;

Fig. 2 schematically represents an architecture of a communication device in which the present invention may be implemented;

Fig. 3 schematically represents an algorithm for obtaining timing references;

Fig. 4 schematically represents an algorithm for instructing a control unit to perform predefined processing at predetermined instants;

Fig. 5 schematically represents an algorithm for providing timing information;

Fig. 6 schematically represents an algorithm for performing predefined processing at predetermined instants;

Fig. 7 schematically represents an architecture of a communication device for performing predefined processing at predetermined instants.

Fig. 1 schematically represents a communication device 100 in which the present invention may be implemented.

Preferably, the communication device 100 is a mobile station (MS), also referred to as user equipment (UE), and the transmitter device is a base station, a base transceiver station (BTS) or a Node B of a Universal Mobile Telecommunications System (UMTS). Alternatively, the receiver device may also be a modem device, which may be installed as part of a MS or UE, but may be also a separate module, which can be attached to various devices.

The communication device 100 comprises a first communication unit 101 and a second communication unit 102 interconnected by a communication link 103.

In a preferred embodiment, the first communication unit 101 is a baseband integrated circuit (BBIC) and the second communication unit 102 is a radio frequency integrated circuit (RFIC). It can be noticed that the chip including the radio frequency processing may comprise part of the baseband processing. The chip incorporating the baseband processing may further comprise application processing. Moreover, the communication link 103 is of DigRF type, for instance according to the DigRF Specification, which supports triple-mode 3 GPP 3G (UMTS) 1 2.5G (EGPRS, Enhanced General Packet Radio Service) / LTE (Long Term Evolution) over a common interface. The first communication unit 101 comprises a first control unit 111, a first clock generator 110 and a first interface unit 112 interfacing the first communication unit 101 with the communication link 103. The second communication unit 102 comprises a second control unit 121, a second clock generator 120 and a second interface unit 122 interfacing the second communication unit 102 with the communication link 103.

The first 101 and second 102 communication units belong to distinct clock domains, defined by clocks CLK l and CLK 2 respectively generated by the first 110 and second 120 clock generators. In other words, the clock CLK l is the clock reference for the first communication unit 101 and the clock CLK 2 is the clock reference for the second communication unit 102. For instance, the clock CLK l runs at 38,4 MHz and the clock CLK 2 runs at 104 MHz or at 124,8 MHz.

The first 112 and second 122 interface units use yet other clock domains based on the same frequency to allow data exchanges between the first 101 and second 102 communication units. No clock domain change therefore occurs between the first 112 and second 122 interface units.

The first control unit 111 is adapted, or configured, to instruct the second control unit 121 to perform predefined processing at predetermined instants. Such predefined processing is for instance related to initiating reception sampling at an accurate instant, which is of importance for OTDoA, or for initiating transmission sampling at an accurate instant, which is of importance for resuming transmission after a gap without causing a false detection of transmission timing adjustment. This aspect is further detailed hereafter with regard to Figs. 4 and 6.

In order to allow the first control unit 111 to accurately instruct the second control unit 121 to perform such predefined processing at predetermined instants, timing references are obtained by the first communication unit 101. This aspect is further detailed hereafter with regard to Figs. 3 and 5.

Fig. 2 schematically represents an architecture of a communication device in which the present invention may be implemented.

According to the shown architecture, the communication device comprises the following components interconnected by a communications bus 210: a processor, microprocessor, microcontroller or CPU {Central Processing Unit) 300; a RAM (Random-Access Memory) 201 ; a ROM (Read-Only Memory) 202; an SD (Secure Digital) card reader 203, or any other device adapted to read information stored on storage means; a communication interface 204. The communication interface 204 allows the communication device to wirelessly communicate with at least one other communication device. The communication interface 204 is for instance an RFIC, or a combination of an RFIC and a BBIC. The communication link 103 may therefore be part of the communications bus 210, be a supplementary transmission line or be included in the communication interface 204.

CPU 200 is capable of executing instructions loaded into RAM 201 from ROM 202 or from an external memory, such as an SD card. After the communication device has been powered on, CPU 200 is capable of reading instructions from RAM 201 and executing these instructions. The instructions form one computer program that causes CPU 200 to perform some or all of the steps of the algorithms described hereafter with regard to Figs. 3 and 4, and/or Figs. 5 and 6.

Any and all steps of the algorithms described hereafter with regard to Figs. 3 and 4, and/or Figs. 5 and 6, may be implemented in software by execution of a set of instructions or program by a programmable computing machine, such as a PC {Personal Computer), a DSP {Digital Signal Processor) or a microcontroller; or else implemented in hardware by a machine or a dedicated component, such as an FPGA {Field-Programmable Gate Array) or an ASIC {Application-Specific Integrated Circuit).

In other words, the communication device includes circuitry, or a device including circuitry, causing the communication device to perform the steps of the algorithms described hereafter with regard to Figs. 3 and 4, and/or Figs. 5 and 6. Such a device including circuitry causing the communication device to perform the steps of the algorithms described hereafter with regard to Figs. 3 and 4, and/or Figs. 5 and 6, may be an external device connectable to the communication device. Such communication device may also be installed as part of another device. In example, this kind of installation would be useful when the communication device is in form of a chip, a chipset, or a module. Alternatively, the communication device according to the invention may provide communication capability to any suitable device, such as a computer device, a machine, in example, a vending machine, or a vehicle like a car or truck, where the communication device may be installed in or connected to for this purpose. The term circuitry refers either to hardware implementation, consisting in analogue and/or digital processing, or to a combination of hardware and software implementation, including instructions of computer program associated with memories and processor causing the processor to perform any and all steps of the algorithms described hereafter with regard to Figs. 3 and 4, and/or Figs. 5 and 6.

Fig. 3 schematically represents an algorithm for obtaining timing references. The algorithm is described in the context of the first communication unit 101 instructing the second communication unit 102 to perform predefined processing at predetermined instants.

In a step 300, the first communication unit 101 transmits a timing reference request message to the second communication unit 102 via the communication link 103. For instance, the timing reference request message is a TAS {Time-Accurate Strobe) message with a specific identifier allowing distinguishing this timing reference request message from other messages. Let's denote TAS 0 this timing reference request message.

In a following step 301, the first communication unit 101 obtains information representative of the instant at which TAS 0 is transmitted to the second communication unit 102, which is represented according to the clock CLK l generated by the first clock generator 110. Let's denote to_,cu _l the instant at which TAS 0 is transmitted according to the clock CLK l .

In a following step 302, the first communication unit 101 obtains information representative of the instant at which TAS 0 is received by the second communication unit 102, which is represented according to the clock CLK 2 generated by the second clock generator 1201. Let's denote to_,cu 2 the instant at which TAS 0 is received according to the clock CLK 2. Information representative of to_,cu 2 is transmitted by the second communication unit 102, as detailed hereafter with regard to Fig. 5. The presented order of the steps 301 and 302 doesn't exclude that to,cLK_2 is obtained prior to to,cLK__l- Indeed, such values may be stored in memory zones and then read from the memory zones in whatever order.

According to a variant, the first communication unit 101 obtains to_,cu 2 from a memory zone shared with the second communication unit 102. In this case, to_,cu 2 is stored by the second communication unit 102 in the shared memory zone and is then obtained by the first communication unit 101, when needed, by reading to_,cu _2 from the shared memory zone. The shared memory zone may also be used to exchange information in the other direction if needed.

With the information representative of to_,cu _l ^and of to_,cu 2, the first communication unit 101 is able to later provide instructions to the second communication unit 102 to perform predefined processing at predetermined instants, as detailed hereafter with regard to Figs. 4 and 6.

Fig. 4 schematically represents an algorithm for instructing a control unit to perform predefined processing at predetermined instants. The algorithm is described in the context of the first communication unit 101 instructing the second communication unit 102 to perform predefined processing at predetermined instants.

In a step 400, the first communication unit 101 determines that the second communication unit 102 shall perform a predefined processing at a predetermined instant. The first communication unit 101 knows at which instant, according to the clock CLK l, this processing shall be performed by the second communication unit 102. The first communication unit 101 prepares a processing request message to be transmitted to the second communication unit 102. For instance, the processing request message is a TAS message. Let's denote TAS_N the processing request message.

It can be noted that a TAS message is preferably transmitted along with at least one control message, associated with said TAS message, and conveying parameters to be used for the processing to which the TAS message is referring.

The first communication unit 101 obtains information representative of an instant at which TAS N is scheduled for transmission to the second communication unit 102, according to the clock CLK l . In a variant, the first communication unit 101 obtains information representative of an instant at which TAS N is transmitted to the second communication unit 102, according to the clock CLK l . Let's denote tN,cLK_l the instant at which TAS N is scheduled for transmission or transmitted to the second communication unit 102.

In a following step 401, the first communication unit 101 obtains, on the basis of to,CLK_ to,CLK_2 and tN,cLK_l an information representative of the instant at which the second communication unit 102 shall perform the predefined processing, according to the clock CLK 2. For instance, such information is the instant at which the second communication unit 102 shall perform the predefined processing, according to the clock CLK 2. In a variant, such information is the instant at which the second communication unit 102 shall consider having received TAS N, according to the clock CLK 2; then, the second communication unit 102 applies a predefined waiting time before performing the predefined processing, such predefined waiting time being known by the first communication unit 101. Let's denote tN,cLK 2 the instant at which the second communication unit 102 shall consider having received TAS N, according to the clock CLK 2.

The instant ΪΝ,( Κ_2 may be expressed as follows:

tN,CLK_2 = to,CLK_2 + (tN,CLK_l ^~ to,CLK_l)

In a following step 402, the first communication unit 101 associates TAS N with information representative of tN,CLK 2·

In a following step 403, the first communication unit 101 transmits TAS N with the associated information representative of the instant at which the second communication unit 102 shall perform the predefined processing.

For instance, at least one control message referring to TAS N is transmitted to the second communication unit 102 and the associated information representative of the instant at which the second communication unit 102 shall perform the predefined processing is included in said at least one control messages. Such control message(s) may explicitly or implicitly, i. e. by design, refer to TAS_N. Such control message(s) may be transmitted by the first communication unit 101 before or after TAS N over the communication link 103.

In a variant, the associated information representative of tN,cLK 2 is included in said TAS_N.

Fig. 5 schematically represents an algorithm for providing timing information. The algorithm is described in the context of the first communication unit 101 instructing the second communication unit 102 to perform predefined processing at predetermined instants.

In a step 500, the second communication unit 102 receives TAS 0, as transmitted by the first communication unit 101 in the step 300.

In a following step 501, the second communication unit 102 determines the instant at which TAS 0 is received by the second communication unit 102, according to the clock CLK 2. This instant corresponds to to_,cu 2, as already mentioned.

In a following step 502, the second communication unit 102 generates a response to TAS 0, including information representative of to_,cu _2- The second communication unit 102 then transmits the generated response to the first communication unit 101.

Fig. 6 schematically represents an algorithm for performing predefined processing at predetermined instants. The algorithm is described in the context of the first communication unit 101 instructing the second communication unit 102 to perform predefined processing at predetermined instants.

In a step 600, the second communication unit 102 receives TAS N, as transmitted by the first communication unit 101 in the step 403. The second communication unit 102 stores the information comprised in control messages associated with TAS_N and transmitted along with TAS_N, or comprised in TAS_N.

In a following step 601, the second communication unit 102 obtains information representative of the instant at which TAS_N shall be processed by the second communication unit 102, in order to perform the predefined process instructed by the first communication unit 101.

Referring to the details already provided with regard to Fig. 4, the second communication unit 102 obtains information representative of the instant at which TAS N shall be processed by extracting such information from at least one control message referring to TAS N and transmitted by the first communication unit 101. In a variant, the second communication unit 102 obtains information representative of the instant at which TAS N shall be processed by extracting such information from TAS_N.

In a following step 602, the second communication unit 102 sets a timeout up, on the basis of the information representative of the instant at which TAS N shall be processed. This timeout is then associated with TAS N. The timeout may be defined as a time delay or as an absolute value of a clock counter representing time in the clock domain CLK 2.

In a following step 603, upon expiration of the timeout, the second control unit 121 performs the predefined process, identified by TAS_N, as instructed by the first communication unit 101. In other words, the second control unit 121 triggers an execution of the predefined processing. The process is then performed at an instant as instructed by the first communication unit 101, despite that the first 101 and second 102 communication units belong to distinct clock domains.

In a particular embodiment, the second communication unit 102 stores in a register, each time a TAS message is received, the value of the clock counter representing time in the clock domain CLK 2. It allows performing the process described hereinbefore with regard to steps 600 to 603 for some TAS messages and not for some others, depending on the time accuracy needed to perform the processing to which the TAS message is referring. Indeed, as already mentioned, the timing accuracy provided when performing the steps 600 to 603 is particularly useful to initiate reception sampling at an accurate instant or for initiating transmission sampling at an accurate instant. However, the timing accuracy may be relaxed for other processing. Therefore, the second communication unit 102 stores in a register, each time a TAS message is received, the value of the clock counter representing time in the clock domain CLK 2. When the timing accuracy provided when performing the steps 600 to 603 is necessary, the second communication unit 102 then overwrites the value stored in the register. A TAS message can be distinguished from one another thanks to an identifier contained in said TAS message. It allows simplifying the design of the second communication unit 102, as detailed hereafter with regard to Fig. 7.

In an embodiment, the information representative of the instant at which the second communication unit 102 shall perform the predefined processing is the instant at which the second communication unit 102 shall perform the predefined processing. Therefore, the second communication unit 102 waits that a clock counter representing time in the clock domain CLK 2 reaches the value representative of said instant, and perform the predefined processing.

In another embodiment, the information representative of the instant at which the second communication unit 102 shall perform the predefined processing is a value that the clock counter representing time in the clock domain CLK 2 shall have when the instant at which the second communication unit 102 shall perform the predefined processing is reached.

In yet another embodiment, the information representative of the instant at which the second communication unit 102 shall perform the predefined processing corresponds to a predefined number K of the least significant bits of value that the clock counter representing time in the clock domain CLK 2 shall have when the instant at which the second communication unit 102 shall perform the predefined processing is reached.

Let's denote t'_N,cLK ₂ the instant at which TAS_N is received by the second communication unit 102, according to the clock CLK 2. TAS N having some absolute accuracy ±τ, then:

t'N,CLK_2 - T < tN,CLK_2≤ t'N,CLK_2

Let's denote T'_N,C_{LK 2} the value stored in the register, and let's denote T_N,C_{LK 2} the value that the register should have if t'_N,cLK ₂ was equal to t_N,cLK ₂. Let's further denote LT_N,_{CLK 2} the information associated to TAS N that is representative of tN,cLK 2, wherein LTN.CLK 2 corresponds to the K least significant bits of T_N,CLK 2, wherein K is chosen such that:

2^K > 2^Xx/x_counter 2

wherein T_C0Unter 2 denotes the granularity of the clock counter representing time in the clock domain CLK 2.

Therefore, there is an integer Q such that:

TN,CLK_2 ⁼ Q^X2^K + LTN,CLK_2

Moreover :

T'N,CLK_2 - T/T_Counter_2≤ TN,CLK_2 + nXP_counter_₂≤ T'N,CLK_2 + T/T_COunter_2

wherein P counter 2 is the period of the counter expressed as a number of T_C0Unter 2, the period of a counter being the number of cycles necessary to reach again a same value.

Therefore :

T'N,CLK_2 - T/T_Counter_2≤ Q^X2^K + LTN,CLK_2 ≤ T'N,CLK_2 + t/T_COUnter_2

and :

(T'N,CLK_2 - LTN.CLK_2)/ 2^K - τ/(2^Κ T_COUnter_2)≤ Q + n^XPcounter_2 2^K

≤ (T'N,CLK_2 - LTN,CLK_2)/ 2^K + τ/(2^Κ T_COunter_2)

According to the aforementioned definition of :

τ/(2^Κ T_counter_2) < 0.5

Therefore, Q is the closest integer to (T'N.CLK 2 - LT_N,CLK ₂)/2 modulo counter ₂/2^K:

Q = floor((T'N,cLK 2 - LTN,CLK ₂)/2^K + 0.5) modulo ^ counter ₂/2

Therefore the value L T_N,CLK 2 rather than T_N,CLK 2 is advantageously transmitted in association with TAS_N, with the advantage of transmitting fewer bits over the communication link 103.

The second communication unit 102 is then able to determine TN,CLK 2, as stated above, on the basis of LT_N,CLK 2. In this case, the first communication unit 101 transmits as such information the K less significant bits of such counter value. The most significant bits then are computed on the basis of the value T'_N,CLK 2 as stored by the second communication unit 102 when receiving TAS N.

In a preferred embodiment, the first communication unit 101 refreshes the values to,cLK 1 and to,cLK 2· This may be performed on a regular basis. The refresh period is in that case such that the values to,cLK__l and to_,cu _2 are not used without refresh longer than the period of a counter used to represent the time in the clock domain CLK l . In other words, refreshing the values to,cLK__l and to_;cLK_2 is performed on the basis of a period of a counter used to define the instants according to the first clock reference.

The values representative of to,cLK__l and to_;cLK_2 are refreshed by adding a shift value to each of them. Let's denote T₀,C_LK i and T₀,C_{LK 2} those values respectively. T₀,cLK 1 is an integer and is initially the value of the counter used to represent the time in the clock domain CLK l . T_O,_{CLK 2} is a rational number and is a multiple of F₂/(Fi v F₂), where Fi and F₂ are the clock frequencies of CLK l and CLK 2 respectively, and Fi v F₂ denotes their least common multiple. T_O,_{CLK 2} is initially an integer that is the value of the counter used to represent the time in the clock domain CLK 2. Let's further denote P_COunter 1 and P_COunter ₂ the periods of the counters used to represent the time in the clock domains CLK l and CLK 2 respectively, expressed as number of 1/Fi and 1/F₂ granularities respectively.

Considering that the refresh occurs roughly N cycles of the clock CLK l after the previous one, then T₀,CLK 1 is replaced by (T₀,CLK 1 + N) modulo P_COunter 1 and T₀,cLK_2 is replaced by (T₀,CLK_2 + NxFi/F₂) modulo P_COunter_2.

It can be noticed that refreshing the values to,cLK__l and to,cLK_2 don't require any further exchange between the first 101 and second 102 communication units.

Fig. 7 schematically represents an architecture of the second communication unit 102 in a particular embodiment.

The second control unit 121 comprises a TAS input FIFO 721 and a control input FIFO 722. The TAS messages received via the second interface unit 122 are stored in the TAS input FIFO 721, and control messages received via the second interface unit 122 are stored in the control input FIFO 722. As already mentioned, such control messages may refer to a TAS message. They may also be independent from any TAS message; in this case, they allow the first communication unit 101 to configure the second communication unit 102, with no specific timing constraint.

Upon storing a TAS message in the TAS input FIFO 721, an interrupt triggers an interpreter 724. The same applies upon storing at least one control message in the control input FIFO 722. The interpreter 724 is in charge of interpreting the TAS messages and the control messages received via the second interface unit 122. The interpreter 724 identifies the processing to be performed by the second communication unit 102 in response to the TAS messages and/or control messages, schedules such processing and configures the second communication unit 102 to perform the processing at the scheduled instants. To achieve this, the interpreter 724 configures an event manager 723. For flexibility considerations in the evolution of the interpretation of the TAS messages and control messages, the operations performed by the interpreter 724 are performed in software. The interpreter 724 therefore relies, at least for a part of its operation, on a processor and a set of instructions in the form of a computer program.

In a preferred embodiment, the first communication unit 101 transmits TAS N before any control message referring to TAS_N. The interpreter 724 is able to instruct the event manager 723 to schedule an event, triggering the execution of the process to which TAS_N refers, in a more flexible way. Indeed, it allows the event manager 723 to define events to be scheduled using an absolute value of the clock counter representing time in the time domain CLK 2, as explained hereafter.

Upon storing a TAS message in the TAS input FIFO 721 , the event manager

723 is triggered and stores in a register the value of the clock counter representing time in the time domain CLK 2. Thus, this process is identical whatever the type of TAS message is.

When TAS N is received by the second communication unit 102, the interpreter

724 instructs the event manager 723 to update the register in which the value of the clock counter representing time in the time domain CLK 2 has been stored upon storing TAS_N. The interpreter 724 may also update the register on its own. The updated value is defined on the basis of the information representative of the instant at which the process has to be performed according to the clock reference CLK 2, as received from the first communication unit 101.

In a preferred embodiment, plural control messages follow TAS N to which said control messages refer. The first control message in sequence comprises the information representative of the instant at which the process has to be performed by the second communication unit 102, namely TN,C_LK_₂ or LTN,C_{LK 2} in the embodiment detailed above. The control messages may comprise at least one parameter related to said process to be performed by the second communication unit 102. Such a parameter may be comprised in the first message in sequence and/or in a following control message in sequence. In a particular embodiment, the first message in sequence comprises the information representative of the instant at which the process has to be performed by the second communication unit 102 and the at least one following control message in sequence comprises said at least one parameter related to said process to be performed by the second communication unit 102. For instance such parameters represent a value of a gain to be setup. In this way, the event manager 723 sets in a register the value of the clock counter representing time in the time domain CLK_2 identifying the instant at which TAS-N has been received, then the first control message in sequence is interpreted by the interpreter 724, which causes the register to be overwritten according to the information contained in this first control message. Then, the interpreter 724 interprets the following control messages associated with TAS N in order to define the process to be performed by the second communication unit 102 and the relative time(s) at which this process shall be performed, the relative time representing the delay between the instant represented by the value in the register and the instant at which the process shall be performed. Such relative time may be predefined according to TAS N and/or at least one parameter contained in the control messages associated with TAS N. Then the interpreter 724 instructs the event manager 723 to schedule at least one event, triggering the execution of said process by the second communication unit 102, by providing said relative time(s). The event manager 723 is therefore able to schedule such events, in absolute time, by reading the value stored in the register and adding to the read value the relative time(s) provided by the interpreter 724.

The description hereinbefore has been detailed in a context in which the first communication unit 101 obtains information representative of the instant to,cu l at which TAS 0 is transmitted to the second communication unit 102 and obtains, e.g. receives from the second communication unit 102, information representative of the instant to,cu 2 at which TAS 0 is received by the second communication unit 102. Moreover, in this context, the first communication unit 101 obtains information representative of the instant tN,cLK_l at which TAS_N is transmitted or scheduled for transmission to the second communication unit 102. Then, the first communication unit 101 obtains, on the basis of to,cLK_ ¾,(χκ_2 and t^cLK l_? information representative of the instant t^_^cLK 2 at which the second communication unit 102 shall perform the predefined processing. Then, the first communication unit 101 transmits the information representative of the instant t^_^cLK 2 to the second communication unit 102.

In another embodiment, the second communication unit 102 obtains, e.g. receives from the first communication unit 101, information representative of the instant to,cu l at which TAS 0 is transmitted to the second communication unit 102. The second communication unit 102 obtains information representative of the instant to,CLK_2 at which TAS O is received by the second communication unit 102. Then, the second communication unit 102 obtains, e.g. receives from the first communication unit 101, information representative of the instant t^cLK _l at which TAS N is transmitted or scheduled for transmission by the first communication unit 101. Then, the second communication unit 102 obtains, on the basis of to,cLK_ to_,cu _2 and tN,CLK an information representative of the instant t^_^cLK 2 at which the second communication unit 102 shall perform the predefined processing.

In yet another embodiment, a third unit distinct from the first and second communication units but connected to the first and second units obtains, e.g. receives from the first communication unit 101 , information representative of the instant to,CLK l at which TAS O is transmitted to the second communication unit 102. The third unit then obtains, e.g. receives from the second communication unit 102, information representative of the instant to_,cu 2 at which TAS O is received by the second communication unit 102. Then, the third unit obtains information representative of the instant tN,cLK_l at which TAS_N is transmitted or scheduled for transmission by the first communication unit 101. Then, the third unit obtains, on the basis of to,cLK_ to,CLK_2 and t^cLK l _? an information representative of the instant tN,CLK 2 at which the second communication unit 102 shall perform the predefined processing. Then, the third unit transmits the information representative of the instant tN,CLK 2 to the second communication unit 102.

Claims

1. A method for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, characterized in that said method comprises:

- obtaining first information representative of an instant at which a timing reference request message is transmitted by the first communication unit, according to the first clock reference;

- obtaining second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- obtaining third information representative of an instant at which a processing request message is transmitted or has to be transmitted by the first communication unit, according to the first clock reference; and

- determining fourth information representative of an instant at which said predefined process has to be performed by said second communication unit according to said second clock reference, said fourth information being determined on the basis of the obtained first, second and third information.

2. The method according to claim 1, characterized in that said method causes the first communication unit to perform:

- transmitting the timing reference request message;

- determining said first information representative of the instant at which the timing reference request message is transmitted, according to the first clock reference;

- receiving said second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- transmitting the processing request message instructing the second communication unit to perform the predefined processing;

- determining said third information representative of the instant at which the processing request message is transmitted or has to be transmitted, according to the first clock reference; and - transmitting the fourth information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference.

3. The method according to claim 2, characterized in that said method causes the second communication unit to perform:

- receiving the timing reference request message;

- determining the second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference; and

- transmitting a timing reference response message including said second information.

4. The method according to claim 3, characterized in that said method causes the second communication unit to further perform:

- receiving the processing request message;

- receiving the fourth information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference; and

- triggering an execution of the predefined processing, on the basis of the received fourth information.

5. The method according to claim 1, characterized in that said method causes the second communication unit to perform:

- receiving the timing reference request message;

- receiving said first information representative of the instant at which the timing reference request message is transmitted, according to the first clock reference;

- determining said second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- receiving the processing request message instructing the second communication unit to perform the predefined processing; - receiving said third information representative of the instant at which the processing request message is transmitted or has to be transmitted, according to the first clock reference; and

- determining the fourth information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference.

6. The method according to any one of claims 1 to 5, characterized in that said processing request message is of time accurate strobe type and in that said fourth information is included in a control message referring to said processing request message.

7. The method according to claim 6, characterized in that said control message is transmitted after said processing request message.

8. The method according to claim 7, characterized in that plural control messages referring to said processing request message are transmitted after said processing request message, and in that the first control message in sequence comprise said fourth information and in that the control messages further comprise at least one parameter related to said predefined process that has to be performed by said second communication unit..

9. The method according to any one of claims 1 to 8, characterized in that said method causes the second communication unit to further perform :

- storing a first value of a counter representing time according to the second clock reference, wherein said first value identifies the instant at which said processing request message is received by said second communication unit according to said second clock reference;

- determining a second value of the counter representing time according to the second clock reference, wherein said second value identifies the instant at which said predefined process has to be performed by the second communication unit, said second value being determined on the basis of at least said fourth information; and

- overwriting the stored first value by said second value.

10. The method according to claim 9, characterized in that said fourth information corresponds to a predefined number of the least significant bits of a value of the counter representing time according to the second clock reference,

and in that said method causes the second communication unit to further perform:

- reading said stored first value; and

- determining the second value of the counter representing time according to the second clock reference on the basis of the stored first value and of said fourth information.

11. The method according to any one of claims 1 to 9, characterized in that said fourth information corresponds to a value of a counter representing time according to the second clock reference.

12. The method according to any one of claims 1 to 11, characterized in that said method comprises refreshing the first and second information by adding a shift value to each of said first and second information.

13. The method according to claim 12, characterized in that refreshing the first and second information is performed on the basis of a period of a counter representing time according to the first clock reference and used to define the instants represented by the first and third information according to the first clock reference.

14. The method according to any one of claims 1 to 13, characterized in that said first communication unit is a baseband integrated circuit and said second communication unit is a radio -frequency integrated circuit.

15. A method for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, characterized in that said method causes the second communication unit to perform:

- receiving a timing reference request message; - determining an information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- transmitting a timing reference response message including said second information;

- receiving a processing request message;

- receiving an information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference; and

- triggering an execution of the predefined processing, on the basis of the information representative of the instant at which said predefined process has to be performed.

16. The method according to claim 15, characterized in that said method causes the second communication unit to further perform:

- storing a first value of a counter representing time according to the second clock reference, wherein said first value identifies the instant at which said processing request message is received by said second communication unit according to said second clock reference;

- determining a second value of the counter representing time according to the second clock reference, wherein said second value identifies the instant at which said predefined process has to be performed by the second communication unit, said second value being determined on the basis of at least said fourth information; and

- overwriting the stored first value by said second value.

17. The method according to claim 16, characterized in that said fourth information corresponds to a predefined number of the least significant bits of a value of the counter representing time according to the second clock reference, and in that said method causes the second communication unit to further perform:

- reading said stored first value; and

- determining the second value of the counter representing time according to the second clock reference on the basis of the stored first value and of said fourth information.

18. A system for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, characterized in that said system comprises:

- means for obtaining first information representative of an instant at which a timing reference request message is transmitted by the first communication unit, according to the first clock reference;

- means for obtaining second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- means for obtaining third information representative of an instant at which a processing request message is transmitted or has to be transmitted by the first communication unit, according to the first clock reference; and

- means for determining fourth information representative of an instant at which said predefined process has to be performed by said second communication unit according to said second clock reference, said fourth information being determined on the basis of the obtained first, second and third information.

19. The system according to claim 18, characterized in that said system causes the first communication unit to implement:

- means for transmitting the timing reference request message;

- means for determining said first information representative of the instant at which the timing reference request message is transmitted, according to the first clock reference;

- means for receiving said second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- means for transmitting the processing request message instructing the second communication unit to perform the predefined processing;

- means for determining said third information representative of the instant at which the processing request message is transmitted or has to be transmitted, according to the first clock reference; and - means for transmitting the fourth information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference.

20. The system according to claim 19, characterized in that said system causes the second communication unit to implement:

- means for receiving the timing reference request message;

- means for determining the second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference; and

- means for transmitting a timing reference response message including said second information.

21. The system according to claim 20, characterized in that said system causes the second communication unit to further implement:

- means for receiving the processing request message;

- means for receiving the fourth information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference; and

- means for triggering an execution of the predefined processing, on the basis of the received fourth information.

22. The system according to claim 18, characterized in that said system causes the second communication unit to implement:

- means for receiving the timing reference request message;

- means for receiving said first information representative of the instant at which the timing reference request message is transmitted, according to the first clock reference;

- means for determining said second information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- means for receiving the processing request message instructing the second communication unit to perform the predefined processing; - means for receiving said third information representative of the instant at which the processing request message is transmitted or has to be transmitted, according to the first clock reference; and

- means for determining the fourth information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference.

23. The system according to any one of claims 18 to 22, characterized in that said processing request message is of time accurate strobe type and in that said fourth information is included in a control message referring to said processing request message.

24. The system according to claim 23, characterized in that said control message is transmitted after said processing request message.

25. The system according to claim 24, characterized in that said system causes the second communication unit to implement means for transmitting, after said processing request message, plural control messages referring to said processing request message, and in that the first control message in sequence comprises said fourth information and in that the control messages further comprise at least one parameter related to said predefined process that has to be performed by said second communication unit.

26. The system according to any one of claims 18 to 25, characterized in that said system causes the second communication unit to further implement:

- means for storing a first value of a counter representing time according to the second clock reference, wherein said first value identifies the instant at which said processing request message is received by said second communication unit according to said second clock reference;

- means for determining a second value of the counter representing time according to the second clock reference, wherein said second value identifies the instant at which said predefined process has to be performed by the second communication unit, said second value being determined on the basis of at least said fourth information; and - means for overwriting the stored first value by said second value.

27. The system according to claim 26, characterized in that said fourth information corresponds to a predefined number of the least significant bits of a value of the counter representing time according to the second clock reference, and in that said system causes the second communication unit to further implement:

- means for reading said stored first value; and

- means for determining the second value of the counter representing time according to the second clock reference on the basis of the stored first value and of said fourth information.

28. The system according to any one of claims 18 to 27, characterized in that said fourth information corresponds to a value of a counter representing time according to the second clock reference.

29. The system according to any one of claims 18 to 28, characterized in that said system comprises means for refreshing the first and second information by adding a shift value to each of said first and second information.

30. The system according to claim 29, characterized in that said means for refreshing the first and second information are adapted to perform refreshing on the basis of a period of a counter representing time according to the first clock reference and used to define the instants represented by the first and third information according to the first clock reference.

31. The system according to any one of claims 18 to 30, characterized in that said first communication unit is a baseband integrated circuit and said second communication unit is a radio -frequency integrated circuit.

32. A device for causing a first communication unit to instruct a second communication unit to perform a predefined processing, the first communication unit having a first clock reference, the second communication unit having a second clock reference, characterized in that said device comprises:

- means for receiving a timing reference request message; - means for determining an information representative of an instant at which the timing reference request message is received by the second communication unit, according to the second clock reference;

- means for transmitting a timing reference response message including said second information;

- means for receiving a processing request message;

- means for receiving an information representative of the instant at which said predefined process has to be performed by the second communication unit according to said second clock reference; and

- means for triggering an execution of the predefined processing, on the basis of the information representative of the instant at which said predefined process has to be performed.

33. The device according to claim 32, characterized in that it comprises:

- means for storing a first value of a counter representing time according to the second clock reference, wherein said first value identifies the instant at which said processing request message is received by said second communication unit according to said second clock reference;

- means for determining a second value of the counter representing time according to the second clock reference, wherein said second value identifies the instant at which said predefined process has to be performed by the second communication unit, said second value being determined on the basis of at least said fourth information; and

- means for overwriting the stored first value by said second value.

34. The device according to claim 33, characterized in that said fourth information corresponds to a predefined number of the least significant bits of a value of the counter representing time according to the second clock reference,

and in that said device comprises:

- means for reading said stored first value; and

- means for determining the second value of the counter representing time according to the second clock reference on the basis of the stored first value and of said fourth information.