text: for explanatory and exemplifying reasons a base station protocol entity , here comprising a mac - hs entity in a base station arrangement , here on the utran side , or in node - b , will be described with reference to fig1 . generally there is one mac - hs entity in the utran for each cell supporting hs - dsch transmission . this is particularly described in 3gpp ts 25 . 321 chapters 4 . 2 . 4 . 3 and 4 . 2 . 3 . 3 . the mac - hs is responsible for handling the data transmitted on the hs - dsch and for management of the physical resources allocated to hsdpa . mac - hs receives configuration parameters from the rrc layer via the mac control sap and there should be priority handling per mac - d pdu flow in a mac - hs . a mac - hs comprises four different functional entities . one of these entities is the flow control entity which is the companion flow control function to the flow control function in the mac - c / sh / m which will not be further explained herein . this function is intended to limit mac layer 2 signalling latency and reduce discarded and retransmitted data as a result of hs - dsch congestion . flow control is provided independently by mac - d flow for a given mac - hs entity . it further comprises an entity scheduling / priority handling means which is a function managing hs - dsch resources between harq entities and data flows according to their priority . based on status reports from associated uplink signalling either new transmission or retransmission is determined . further it determines the queue id and tsn for each new mac - hs pdu being serviced and in case of tdd ( time division duplex ) the hcsn ( hs - scch cyclic sequence number ) is determined . a new transmission can be initiated instead of a pending retransmission at any time to support the priority handling . hence , a harq process sending a mac - hs pdu waits for an ack ( possibly it resends the mac - hs pdu at nack / dtx etc ., but it is proceeded with the nack process before it gets new data ). a harq process may however be resting if it has received a nack until it performs a retransmission if it has not got a retransmission priority . still another entity is the harq entity which handles the hybrid arq functionality for one user . one harq entity is capable of supporting multiple instances ( harq process ) of stop and wait harq protocols . there should be one harq process per hs - dsch per tti . in other words , if there is a transmission , then a harq process is involved , but there does not have to be a transmission , e . g . if there is no power left for hsdpa compared with normal speed traffic . furthermore it comprises a function denoted trfc selection which handles selection of an appropriate transport format and resource for the data to be transmitted on hs - dsch . fig2 similarly schematically illustrates a mac - hs entity on the ue side . the mac - hs handles the hsdpa specific functions and particularly comprises a harq entity which is responsible for handling the mac functions relating to the harq protocol . the harq functional entity handles all the tasks that are required for hybrid arq . it is responsible for generating acknowledgements or nacks . another entity is the reordering queue distribution entity which is a function that routes mac - hs pdus to the correct reordering buffer based on the queue id of the mac - pdu . the reordering function or the reordering entity reorders received mac - hs pdus according to the received tsn . mac - hs pdus with consecutive tsns are delivered to the disassembly function ( see below ) upon reception . mac - hs pdus are not delivered to the disassembly function if mac - hs pdus with a lower tsn are missing . there is one reordering entity for each queue id configured at the ue . finally , it comprises the disassembly entity which is responsible for disassembling of mac - hs pdus . when a mac - hs pdu is disassembled , the mac - hs header is removed , the mac - d pdus are extracted and any present padding bits are removed . then the mac - d pdus are delivered to higher layer . in case of hs - dsch a mac pdu consists of one mac - hs header and mac - hs payload ( one or more mac - d pdus ), where the payload consists of one or more mac - d pdus from one or several mac - d flows . a maximum of one mac - hs pdu can be transmitted in a tti per ue . the mac - hs header is of variable size and the mac - hs payload in one tti belongs to the same reordering queue . fig3 schematically shows a mac - hs pdu as described in 3gpp ts 25 . 321 chapter 9 . 2 . 1 . in the figure the mac - hs payload is indicated and a mac - hs header which will be further described herein . a mac - hs header comprises a version flag ( vf ) field which is a one bit flag providing extension capabilities of the mac - hs pdu format . it should be set to zero according to the standard . it further comprises a queue identifier , the queue id field , which provides identification of the reordering queue in the receiver in order to support independent buffer handling of data belonging to different reordering queues . the length of the queue id field is 3 bits . it further comprises a transmission sequence number ( tsn ) field which provides an identifier for the transmission sequence number on the mac - hs pdu . the tsn field is used for reordering purposes to support in - sequence delivery to higher layers . the length of the tsn field is 6 bits . subsequently it comprises a size index identifier ( sid ) field which identifies the size of a set of consecutive mac - d pdus . the mac - d pdu size for given sid is configured by higher layers and it is independent for each queue id . the length of the sid field is 3 bits . there is also an n - field identifying the number of consecutive mac - d pdus with equal size . the length of the n - field is 7 bits . in the flag - f - field is a flag indicating if more fields are present in the mac - hs header or not . if the f - field is set to “ 0 ”, the f - field is followed by an additional set of sid , n and f - fields . if the f - field is set to “ 1 ” the f - field is followed by a mac - d pdu . fig4 a describes a mac - hs pdu wherein , according to the present invention , the version field ( vf ) is used as an indication of a mac - hs specific probing or information control message , in the following also briefly denoted mac - hs control message or simply control message ( frame ). probing is a mechanism where node - b initiates a mac - hs transmission , where mac - hs payload does not consist of mac - d data . the mac - hs payload used for probing shall be discarded at the ue mac - hs protocol entity . it can be used to test internal tfrc algorithms against real transmissions or to improve internal tfrc algorithms . it can also be used as an ue polling mechanism to check whether the ue is actually present and ready to receive data . the mac - hs specific control data pdu may be of variable size and number ( n ) to test actual transmission of small tbs ( transport block size ) or large tbs . in this case vf is set to 1 . in this embodiment interpretation of the other fields would be that the queue id indicates to which queue this specific control message refers , tsn is unused and the sid fields may be unused or set to a default value for control messages , or to different values if different sizes of control messages are used . the n and f fields operate normally , i . e . as described with reference to fig3 . according to the invention vf = 1 directly indicates that there is a specific information control message according to the invention . since vf concerns the whole packet , no “ conventional ” user data can be sent , different from the implementation described with reference to fig5 wherein a sid field is used as an indication of a specific information control message . if only one of the sid frames is given a specific value , the others may relate to “ conventional ” data . if all sid frames are given the specific value , only a specific information control message can be sent as in fig4 a . fig4 b describes a mac - hs pdu wherein , according to another embodiment of the present invention , the indication of a mac - hs specific probing message is signalled by the presence of only one sid / n and f set , and whereas n is set equal to 0 . the complete space of the mac - hs payload shall be used for signalling of the mac - hs specific control frame , and may be of variable size to test actual transmission of small tbs up to large tbs . it can be noted that when the content of the mac - hs specific control frame is equal to padding this is an indication of a probing control frame . thus , according to the embodiment shown in fig4 b vf = 0 , n = 0 and f = 1 . the queue identity may be a legitimate queue identity for a mobile user station , sid may also be indicated in a normal manner . there is however only one set of sid / n / f . a receiver will then receive the packet in a normal way , but the situation is a special situation since n = 0 . if , as in fig4 b , the mac - hs payload , consists of the mac - hs specific control data , no padding at the end , the mobile station will interpret the whole field as data . fig4 c shows another implementation of the embodiment in fig4 b wherein the whole information field only comprises padding . the mobile user station will normally discard it , and may , in particular implementations mark tsn in reordering queue as received and without content . ( alternatively , it is discarded and the reordering queue is not updated ). this will then constitute a probing control frame , or null - data ; i . e . it discloses one way of providing a null data message . fig5 is a figure similar to fig3 and 4a or 4 b , 4 c but illustrating still another embodiment than those described in fig4 a , 4 b , 4 c in which instead of e . g . the vf - field the ( here one ) sid field is used and wherein a specific sid value is an indication of a specific information control message , for example sid 3 ′ b 111 . the operation of the other fields would then be normal operation for all the fields . in particular the mac - hs receiver should interpret the specific control message prior to the mac - hs transmission to the rlc layer . this means that reception must pass the reordering entity of the ue before the specific control message is interpreted . this mechanism can for example be used by node - b to trigger the exceptional handling in the ue ( e . g . timer based stall avoidance ) when for instance node - b has discarded a mac - hs . according to another embodiment similar to the embodiment described with reference to fig5 , the ue shall interpret the specific information control messages prior to delivery to the reordering entity . then the specific information control message would be interpreted immediately by the mac - hs receiver control plane . fig5 , with dotted lines , illustrates which sids correspond to which data , i . e . the first sid ( 3 ′ b 111 ) indicates and corresponds to the specific control data whereas the other sids ( sid 2 , . . . , sid k ) relate to n 2 mac - d pdus , size given by sid 2 , . . . , n k mac - d pdus , size given by sid k . fig6 is a schematical block diagram of a ue 10 according to the present invention . it should be clear that only those parts or functions that are relevant for the description of the inventive concept are included . downlink traffic to the ue is received over the hs - scch for control signalling and the hs - pdsch for packet payload . the control signalling slightly precedes the actual payload such that the ue can get prepared to receive the packet payload . in hs - scch decoding means 11 an incoming message ( on the hs - scch control channel ) for example the identity of the mobile station ue is used to establish if the ue message is appropriately received by the correct ue . from hs - scch , if the control message is appropriately decoded or successfully decoded , it is known to which harq process in the harq entity 12 the mac - hs pdu should be directed . if also the harq process can be successfully decoded , and a mac - hs pdu is successfully decoded , it is known to which queue in the reordering and disassembly entity 13 it should be provided . it is then established if it can be forwarded to the rlc layer , 17 , however , it is also established in the mac - hs control message handler 16 if the mac - hs pdu is a specific control message , or a control mac - hs pdu . this can be done in different manners as briefly described with reference to the flow diagrams 8 - 12 below but also in any other appropriate manner . if the harq process is successfully decoded , information thereon is provided to ue feedback processing means 14 which forwards the relevant information to layer 1 processing means 15 which maps the relevant message on an uplink hs - dpcch channel for transmission to for example node - b . generally the specific control message according to the invention is included in the mac - hs pdu and acknowledgement that a harq process has been successfully decoded may also serve as an indirect indication that the specific control message has been received . this is no explicit or direct acknowledgement that the specific control message has been received , but since the mac - hs pdu has been successfully decoded etc ., also the specific control message will have been observed . the inventive concept is however not limited to the provisioning of any acknowledgements whatsoever , but also simply covers sending a specific control message to the mobile station from the base station . however , in some implementations the specific control message may be of different types . it may for example consist of a reset message resetting all harq processes and queues . such a procedure is indicated with dashed lines in the figure , a 1 - a 4 , i . e . the harq entity 12 has to be notified by the control message handler 16 that all processes should be reset a 1 . also the reordering and disassembling entity 13 has to be informed thereon , a 2 , or instructed to reset all queues . an indication that everything has been reset also has to be provided , a 3 , to rlc 17 . then however , some active response acknowledgement to the base station ( node - b ) is normally required and of course a dedicated or specific channel can be used for that purpose . as an alternative thereto the cqi processing means 17 can be used as a return channel , a 4 , for example on a time division basis . the cqi processing means 17 communicates with layer 1 processing means 15 mapping the message on the uplink hs - dpcch channel as described above . it should be clear that the mac - hs control message handler 16 also could have been provided between the harq entity 12 and the reordering and disassembly entity 13 . also for a null data message ( probing message ) the response ( e . g . acknowledgement ) to node - b could be done via cqi processing means 17 but the simplest way is to use in any case normally sent messages which are provided , for example if the harq process decoding was successful or not , if the hs - scch decoding was successful or not , which hence means that already “ existing ” acks / nacks are used as indirect indications . fig7 is a block diagram describing those functions of a base station arrangement 20 , here umts node - b , which are necessary for the functioning of the present invention . for reasons of clarity all other functions etc . are omitted . on the uplink , from ues sent control messages are received over hs - dpcch whereas for downlink traffic , control packets or control messages are sent over hs - scch and payload over hs - pdsch . node - b 20 comprises a number of buffers 23 1 , . . . , 23 n ; one input buffer per ue and per served queue . as discussed above it also comprises a number of harq entities , 22 1 , . . . , 22 n , one harq entity for each ue . each harq entity in turn comprises a number of harq processes , here it is supposed to be m processes for each ue . node - b also comprises a layer 1 receiver 21 for e . g . receiving messages from the ues , ue feedback decoder 24 e . g . decoding acks or nacks or dtx . dtx means that neither the control ( also conventional ) messages nor payload has been correctly received / decoded by an ue . this information is provided by decoder 24 to all harq entities 22 1 , . . . , 22 n and , to the scheduler 28 . if the specific control message according to the present invention requires an action , i . e . it is for example a reset message etc . as briefly mentioned above and as will be further discussed below , particularly with reference to fig1 , the specific control message , or rather a response thereto from an ue , is e . g . provided for example by the cqi channel as discussed with reference to fig6 . the scheduler 28 is the central part of the node - b which optionally only handles control messages , i . e . no payload , and it is also in communication with the mac - hs control message handler 26 providing specific probing or information control messages according to the invention , also simply denoted specific control messages . the scheduler provides messages to layer 1 processing means 25 over the appropriate harq 22 1 , . . . , 22 n as indicated by the switch acting as an input to layer 1 processing means 25 . only ( substantially ) control information is provided from the input buffer queues 23 1 , . . . , 23 n to scheduler 28 whereas the payload , e . g . mac - hs pdu payload , is provided from the input buffers to the appropriate harq process 22 1 , . . . , 22 n . the scheduler 28 is capable of handling the information about specific control messages ( and responses ), according to the invention an indication of which for example only is contained in the mac - hs header , e . g . in one field thereof for example the vf field or a sid field or n field as discussed above . “ iub ” in the figure illustrates the iub interface . cqi processing means or cqi decoder 27 receives information from layer 1 receiver 21 and provides information to the scheduler 28 related to channel quality estimates etc . fig8 is a very schematical flow diagram describing the inventive concept . thus , for some reason , as discussed earlier , it is supposed that node - b decides to send a specific control message , 1001 . the specific control message itself is then included in the mac - hs pdu payload , whereas in the header an indication thereof is provided in one ( or more ) field ( s ) thereof , 1002 . the mac - hs pdu is then transmitted over the control channel ( hs - scch ) and physical data channel ( hs - pdsch ) to the ue , 1003 . if the mac - hs pdu can be successfully decoded ( cf . e . g . fig9 ) or not , gives rise to the sending of an ack or a nack , 1004 , to node - b . then it is established or detected if the mac - hs pdu ( header ) contains a specific control message indication , 1006 . if yes , it is determined if an action is required ( if several types of specific control messages can be used , i . e . such requiring an action and such that do not require an action ), 1007 . ( i . e . the ue shall first detect if the specific control message indication is provided , and then handle the control data itself .) if not , the ack / nack sent in step 1004 above serves as an indirect indication as to whether the specific control message has been received in ue or not , 1007 a , and this provides the node - b with the desired information ( e . g . as to availability of the ue ). if an action is required , ue takes the relevant action , 1008 , and provides a response or acknowledgement to node - b ( actively ), 1009 . however , also in some cases the ack / nack of step 1004 may replace an active response . fig9 is a flow diagram describing a procedure in an ue according to a first embodiment . as referred to above with reference to fig6 , it is supposed that a mac - hs pdu control message is incoming , 100 , i . e . first the control message is incoming over the hs - scch and , if the decoding can be appropriately done , the payload follows over the hs - pdsch . thus , first an examination is done to establish whether hs - scch was successfully decoded , 101 , e . g . if using the identity of the mobile user station ( rnti ), i . e . if the hs - scch message was addressed to that mobile user station ( ue ). if not , the procedure is repeated for all other hs - ssch codes that may be used by the node - b . if the decoding of other possible hs - scch codes is unsuccessful the processing will continue in subsequent tti . if however the decoding is successful , i . e . the ue is the correct ue , it is established whether a toggling ndi ( e . g . a flush indicator ) is detected , 102 . however , a mobile user station normally can receive on one of up to four control channels . this means that steps 100 , 101 are repeated for all these control channels , unless , of course , decoding is successful for the first , or the second etc ., in which case it is proceeded with step 102 . a reason for sending on e . g . four control channels is to be able to transmit to up to four ues in the same tti using code multiplexing . from the hs - scch message it can be seen which is the appropriate harq process . ndi toggles between 0 and 1 each time the mac - hs payload in the harq process at the node - b has changed . as long as the packet is retransmitted , it should hence be the same ndi ( 0 or 1 ). if there is a toggling ndi indication , the harq process concerned should be flushed , 103 a , prior to the decoding of the hs - pdsch . if however there is no toggling ndi , or flush , indicated , information stored from previous mac - hs transmit attempts for this harq process can be combined with current incoming hs - pdsch in the attempt to decode the mac - hs pdu , 103 . if not , a nack is generated , 104 a , and the procedure is repeated . it can be noted that concurrent mac - hs transmissions to one and the same ue will occur on the same hs - scch to simplify implementation requirements of the ue ( not shown in figure ). if on the other hand it is established that the harq process has been successfully decoded , an ack is generated , 104 , and the mac - hs pdu is fetched from the harq process in question , 105 . then it is established whether a control mac - hs pdu according to the invention is included , in this embodiment it is established whether in the vf - field vf = 1 in the mac - hs pdu header , 106 . if not , the received mac - hs pdu is delivered to ue reordering handling , 106 a . if on the other hand it is established that vf = 1 , it is established which is the identity of the affected queue ( or queues if the mac - hs pdu contained control messages to more than one queue ), 107 . then the specific control message is interpreted in the queue with the established identity id , here denoted x , 108 . in this case there may be implemented an indirect verification ( ack / nack ) if the specific control message has been received , namely since the specific control message indication is contained in the mac - hs pdu header , and if the hs - scch can be successfully decoded and the harq process also , then the specific control message is received . thus the in step 104 generated ack also serves as an acknowledgement ( indirect ) that the specific control message is included and received . fig1 is a flow diagram describing an embodiment corresponding to fig5 illustrating the case when a specific sid value is used as an indication of a specific control message , wherein the other fields are used as in a normally operating case . steps 200 - 204 , 204 a correspond to steps 100 - 104 , 104 a of fig9 and will therefore not be further discussed here . if however it has been established that the harq process has been successfully decoded and an acknowledgement has been provided to the base station arrangement , e . g . node - b , the received mac - hs pdu that was received is delivered to the correct reordering entity depending on the contained queue id , 205 . this step actually includes a number of steps in the reordering entity of a mobile station ue . this is done in a known manner for example described in 3gpp ts 25 . 321 chapter 11 . 6 . 2 . 3 and the task of the reordering entity is to make sure that all mac - hs pdu packets are delivered in the right order to higher protocol layers . in the respective reordering queue it is thus established whether the mac - hs pdu can be delivered in a correct order to rlc , 206 . if not , it is returned to step 200 . if however the outcome is affirmative , an acknowledgement may be sent ( not shown ) and the mac - hs pdu header is analyzed to establish whether the packet contains a specific control message according to the present invention ( i . e . if there is an indication in the header ). in this case it is supposed that sid = 3 ′ b 111 is the indicator of a specific control message , 207 . if there is no specific control message , the mac - hs pdu is transferred to a disassembling entity where the header is removed , 207 a , and the mac - hs pdu payload is forwarded to the rlc layer , 207 b . if however it is established that there is a specific control message , in a queue with an identity n , which is supposed to be the queue which is relevant for the particular mac - hs pdu , the specific control message is interpreted . it may be a specific control message relating to some action to be taken but it may also be a null data message . in the latter case a normally sent acknowledgement as referred to above , serves as an acknowledgement ( indirect ) that the ue has received the specific control message , and in that manner the base station arrangement would be aware of that fact , 208 . if the specific control message requires some action , a response may be returned “ actively ”. it should be clear , as discussed earlier , that either one , or more , or all sid : s may contain a indicator as described above . if one or more does not , also other data ( i . e . mac - d pdu ) may be contained in the payload . it should be noted that in the embodiment described with reference to fig1 , the mac - hs receiver should interpret the specific control message prior to the mac - hs transmission to the rlc layer . the in - sequence delivery criteria are considered before the message is interpreted ( any possible mac - hs control message must pass the reordering entity in the ue before the specific control message ( s ) is / are interpreted ) and this mechanism can be used by a node - b to trigger an exceptional handling in the ue when for instance node - b has discarded a mac - hs pdu . fig1 shows an embodiment similar to the one described with reference to fig1 but with the difference that the ue ignores the in - sequence delivery , any possible mac - hs control message must not pass the reordering entity in the ue before the specific control message ( s ) is / are interpreted , for control messaging . in this case a specific control message is immediately interpreted by the mac - hs receiver control plane . hence , steps 300 - 304 , 304 a correspond to steps 100 - 104 , 104 a or 200 - 204 , 204 a of fig9 and fig1 . step 305 moreover corresponds to step 205 of fig1 . however , following step 305 , the mac - hs pdu header is analyzed , 306 , to establish if , for example , there is a sid = 3 ′ b 111 , 306 . it should be clear that any other indication than 3 ′ b 111 can be used , this is merely being given as an example . ( e . g . n = 0 could also be used ). if yes , for the relevant queue id the control message is interpreted , 306 a . if not , the sequence delivery order is examined , 307 , i . e . for the respective reordering queue , it is established whether a mac - hs pdu can be delivered in the correct order to rlc , 307 . if not , the procedure ends for this packet . if however , the in - sequence criteria is fulfilled , the mac - hs pdu is sent to the disassembly entity where it is disassembled , i . e . the header is removed , 308 . then the packet mac - hs pdu payload is forwarded to the rlc layer , 309 . fig1 is a block diagram describing possible alternative procedures for different kinds of specific control messages . it should be clear that the inventive concept is not limited to cases where a specific control message comprises or may comprise different types , implementations are possible where the message type only for example comprises null data or only one or more of the other types or still other , not discussed , types . however , fig1 is a flow diagram describing the procedure per receiver queue starting with a step when the control message for a queue n is interpreted , 409 . this may be the step that follows on or corresponds to step 108 ( cf . fig9 ) or the step corresponding to step 208 ( cf . fig1 ) or step 306 a ( cf . fig1 ). it is established whether there is a specific control message received for a queue with the identity n , 408 , ( it should be clear that steps 408 , 409 may be done in any order ). however , supposing that the control message has been interpreted , and it has been established that it is a specific control message of type null data , 410 a , the message is discarded , 411 a . in this case it is particularly supposed that indirect acknowledgement is implemented and the normally existing acknowledgement procedures corresponding to successful decoding as discussed above are taken as an acknowledgement that a specific control ( null ) data message has been received . a message of type null data may for example be used by node - b to test the transmission capability of an ue , i . e . to establish if the ue is available , the reception quality per tbs etc . as an alternative , it may have been established that the specific control message is of type statistic reset , 410 b . then , in the ue the receive statistic ( rec stat ) is fetched , 411 b , and a transmit attempt of rec stat to node - b is ordered , 412 b . finally rec stat is reset , 413 b . this message type may be used by node - b to reset the statistic information calculated in an ue , it may for example be assumed that the ue stores statistic information about the amount of successfully decoded hs - scch and hs - pdsch and / or successful reception of hs - scch , but failure to receive hs - pdsch . the quotient successfully decoded hs - scch / successfully decoded hs - scch and hs - pdsch could be mapped onto the cqi report range 0 , . . . , 31 where 31 is defined as a value very close to 1 and 0 as a value very close to 0 of the quotient . the value could be reported back to node - b at specific returned time occasions when the normal cqi is replaced by the quotient . by sending a statistic reset , ue could flush the two statistical counters . in still another embodiment the message is of type reset , 410 c . this e . g . means that the ue should reset the mac - hs entity for the specific queue or for all queues , 411 c . all harq processes should flush its content and revert to a state equal to the start - up state and all reordering units should be flushed resetting all variables ( e . g . next expected tsn ) to start - up state etc . and it is a considerable action that means that a confirmation back to node - b is required , 412 c . this specific control message is hence used to reset mac - hs pdus , i . e . to set tsn to 0 and to optionally deliver all acknowledged but not yet delivered mac - hs pdus to the rlc layer . the confirmation can be done in the same manner as discussed above for example using the cqi in a time divided manner . still another message type may relate to a status request , 410 d . it is hence supposed that an indication is sent to the rlc layer , 411 d , and the specific control message is then discarded , 412 d . rlc layer is supposed to send a status request message at the reception of the indication . in this case direct or indirect acknowledgement may be implemented as discussed earlier , as well as no acknowledgement at all . the rlc layer operates above the mac - hs protocol in the protocol stack . it is e . g . described in 3gpp ts 25 . 322 v6 . 4 . 0 , radio link control ( rlc ) protocol specification . the rlc layer can operate in three modes , transparent mode ( tm )- unacknowledged mode ( um ) and acknowledged mode ( am ). in am mode incorrectly received pdus ( protocol data units ) discovered by the receiving side are retransmitted by the transmitting side and forms an arq protocol ( automatic repeat request ). an am rlc entity consists of a transmitting side , and a receiving side , where the transmitting side of the am rlc entity transmits rlc pdus and the receiving side of the am rlc entity receives rlc pdus . the am rlc entity resides in the ue and in the rnc . the transmitting side segments and / or concatenates rlc sdus into pdus of a fixed length . the receiving side reassembles received pdus into rlc sdus and transmits to higher layers . in am mode the rlc layer is responsible for in sequence delivery of sdus . the sdu is the data units that are received from / transmitted to the layer above rlc . to facilitate in sequence delivery each pdu is given a sequence number , 0 - 4095 , the transmitter transmits pdus with increasing sequence number modulo 4096 . using the sequence number the receiver can detect a missing pdu and transmit a status message indicating the missing pdu ( or pdus ). the receiver can be configured to transmit a status message upon the detection of a missing pdu . the transmitter can request for status messages by setting a poll flag in the pdu header . the mechanisms by which the transmitter sets the poll flag are among others : when the timer_poll expires , meaning that the transmitter requested for status earlier and initiated a timer_poll to reassure that a response is received . a sender is restricted in the amount of “ outstanding data ” it can transmit until a status confirms the reception to the receiving side . “ outstanding data ” relates to the earliest unacknowledged pdu . selective retransmission is possible , e . g . if status message indicates pdu with sequence number 3 , 6 and 13 are missing , only 3 , 6 and 13 needs to be transmitted . it should be noted that this is of course not the only functionality of the rlc layer , but the other functionalities will not be discussed herein . fig1 is a flow diagram describing one implementation of a flow in a base station arrangement , particularly node - b , for a particular application . in this implementation , node - b initiates transmission of a status req . data control message if a last sent packet has not been acknowledged by the ue , i . e . that the ue did not correctly receive the data , in order to make sure that the last sent data has arrived at the mobile station ue . if node - b is informed that the last sent data was correctly received , node - b will know that the ue would take care of the situation when e . g . a second last sent packet was not correctly received . hence , the procedure is initated and it is established if there is a harq process , the relevant harq process n , is terminated , 501 . if the relevant harq process has terminated , it is examined if there are other active or pending harq processes for the current harq entity , 502 . if yes , it is returned to step 500 again . if not , it is examined whether there has been a successful outcome of the harq process ( here process n ), i . e . if an acknowledgement has been received , 503 . if yes , node - b is made aware of this fact and it is returned to the start position , 500 . if however there has been no acknowledgement , it is examined if the input buffer is empty , 504 . if not , the steps as from 500 are repeated . if the input buffer however is empty , a control mac - hs pdu is sent , here it is supposed that it is a status request , 506 . it may however also be null data . it is in this respect referred to fig1 describing procedures when different types of specific control messages are received in the ue . if a status request type of specific control message is received , the mechanism initiates a procedure from the mac - hs layer to signal to higher layers , the rlc layer , to initiate sending of a report ( status message ) to the sending unit , i . e . the radio network controller . if node - b notices that a packet has not been correctly received , the situation may be that the rlc layer is not aware about the fact that a packet has been discarded . this will be the situation if it is a last packet that was not correctly received . if is not the last one , the mechanism will already have been initiated in the ue to handle this case . it is to provide additional security that node - b affects the mac - hs layer of the mobile station ue to indicate to the rlc layer that a packet has been lost . finally fig1 shows a flow diagram for one embodiment of a procedure in node - b when voice over ip ( voip ) is sent wherein node - b periodically ( e . g . with a constant or varying periodicity between the null data control frames , e . g . 100 ms , 100 ms , 200 ms , 200 ms , 400 ms , 400 ms or any other appropriate ( varying ) periodicities ) sends null data specific control messages to be capable to keep relevant information about the reception conditions of the ue . there is a wait 0 , . . . , x ms box , the intention of which is to be able to control how often a mac - hs pdu packet , e . g . a specific control message of type null data , should be sent to the user equipment . hence , it is supposed that the procedure is initiated , 600 , and it is established whether harq process ( n ) is terminated , 601 . if yes , it is examined if there is any other active or pending harq process for the current harq entity , 602 . if not , a waiting time , any of 0 , . . . , x ms is introduced , 603 , and then it is established whether the relevant input buffer is empty , 604 . if yes , a mac - hs pdu specific control message with null data is transmitted , 605 . it should be clear that other types of control messages ( i . e . probing or information control messages , here also denoted specific control messages ), can be sent and that the way of doing so can be varied in a number of ways . it should not be limited to what has been particularly described in the embodiments but merely by the appended claims . it should also be clear that the procedures of the inventive concept in general are not only applicable to node - b and umts , but they are of course also applicable to other similar systems , nodes etc . also in other aspects the invention is not limited to the particularly illustrated embodiments but it can be varied in a number of ways within the scope of the appended claims .