Optimized system access procedures

A base station subsystem (BSS) and a method are described herein for improving an Access Grant Channel (AGCH) capacity when mobile stations establish an uplink Temporary Block Flow (TBF) triggered by a small data transmission (SDT) or an instant message transmission (IMT). Plus, a mobile station (MS) and a method are described herein for improving the AGCH capacity when the mobile station establishes an uplink TBF triggered by a SDT or an IMT.

TECHNICAL FIELD

The present invention relates to a base station subsystem (BSS) and a method for improving an Access Grant Channel (AGCH) capacity when mobile stations establish an uplink Temporary Block Flow (TBF) triggered by a small data transmission (SDT) or an instant message transmission (IMT). Plus, the present invention relates to a mobile station (MS) and a method for improving the AGCH capacity when the mobile station establishes an uplink TBF triggered by a SDT or an IMT.

BACKGROUND

In the wireless telecommunications field it is anticipated that there will be an ever increasing Common Control Channel (CCCH) congestion problem due to the increase of small data transmissions (SDTs) and instant message transmissions (IMTs) as a result of the Machine-to-Machine (M2M) traffic and the frequent small packet transmissions which are going to be generated by mobile stations (e.g., smart phones). Various solutions to address the CCCH congestion problem and other problems are the subject of the present invention.

ABBREVIATIONS

The following abbreviations are herewith defined, at least some of which are referred to within the following description of the present invention.

AGCH Access Grant Channel

ARFCN Absolute Radio Frequency Channel Number

ATI Additional TBF Information

BCCH Broadcast Control Channel

BSS Base Station Subsystem

CCCH Common Control Channel

CS Circuit Switched

DRX Discontinuous Reception

EGPRS Enhanced General Packet Radio Service

EPCR Enhanced Packet Channel Request

eTFI Enhanced Temporary Flow Identity

eUSF Enhanced Uplink State Flag

FN Frame Number

IA Incoming Access

IE Information Element

LAP Low Access Priority

LLC Logical Link Control

MAC Media Access Control

OSAP Optimized System Access Procedure

PACCH Packet Associated Control Channel

PCH Paging Channel

PDU Packet Data Unit

PFC Packet Flow Context

PRR Packet Resource Request

PUA Packet Uplink Assignment

RF Radio Frequency

RLC Radio Link Control

SI System Information

TBF Temporary Block Flow

TCH Traffic Channel

TDMA Time Division Multiple Access

TLLI Temporary Logical Link Identity

TOI Temporary OSAP Identity

TSC Training Sequence Code

SUMMARY

A base station subsystem (BSS), a mobile terminal (MS) and methods that address the aforementioned CCCH congestion problem by improving the capacity on an AGCH are described in the independent claims of the present application. Advantageous embodiments of the BSS, the MS and methods have been described in the dependent claims of the present application.

In one aspect, the present invention provides a BSS configured to interact with a plurality of MSs and perform a procedure (e.g., the optimized system access procedure) to improve an AGCH capacity. The BSS comprises a processor and a memory that stores processor-executable instructions where the processor interfaces with the memory and executes the processor-executable instructions to enable a broadcast operation, a receive operation, and a send operation. The broadcast operation includes broadcasting a new SI to the plurality of MSs, where the new SI includes an indicator which indicates to the plurality of MSs that the BSS is configured to perform the procedure (e.g., the optimized system access procedure) to improve the AGCH capacity. The receive operation includes receiving at least one access request from at least one of the plurality of MSs, where the at least one MS is requesting to establish an uplink TBF to transmit a SDT or an IMT (note: the MS would send the access request only if the BSS is configured to perform the optimized system access procedure to improve the AGCH capacity). The send operation includes sending, in response to the received at least one access request, an immediate assignment message on the AGCH for the at least one MS, where the immediate assignment message includes static radio parameters and at least a portion of dynamic radio parameters which are to be used along with the static radio parameters by the at least one MS when establishing the uplink TBF to transmit the SDT or IMT. This is an advantage over the prior art because the BSS by broadcasting the new SI which includes the new indicator is now able to send one immediate assignment message to multiple MSs thus improving the AGCH capacity.

In another aspect, the present invention provides a method implemented by a BSS, which interacts with a plurality of MSs, for performing a procedure (e.g., the optimized system access procedure) to improve an AGCH capacity. The method comprises a broadcasting step, a receiving step, and a sending step. The broadcasting step includes broadcasting a new SI to the plurality of MSs, where the new SI includes an indicator which indicates to the plurality of MSs that the BSS is configured to perform the procedure (e.g., the optimized system access procedure) to improve the AGCH capacity. The receiving step includes receiving at least one access request from at least one of the plurality of MSs, where the at least one MS is requesting to establish an uplink TBF to transmit a SDT or an IMT (note: the MS would send the access request only if the BSS is configured to perform the optimized system access procedure to improve the AGCH capacity). The sending step includes sending, in response to the received at least one access request, an immediate assignment message on the AGCH for the at least one MS, where the immediate assignment message includes static radio parameters and at least a portion of dynamic radio parameters which are to be used along with the static radio parameters by the at least one MS when establishing the uplink TBF to transmit the SDT or IMT. This is an advantage over the prior art because the BSS by broadcasting the new SI which includes the new indicator is now able to send one immediate assignment message to multiple MSs thus improving the AGCH capacity.

In another aspect, the present invention provides a MS configured to interact with a BSS and to improve an AGCH capacity. The MS comprising: a processor and a memory that stores processor-executable instructions where the processor interfaces with the memory and executes the processor-executable instructions to enable a first receiving operation, a sending operation, a second receiving operation, and a using operation. The first receiving operation includes receiving a new SI from the base station subsystem, where the new SI includes an indicator which indicates to the MS that the BSS is configured to perform a procedure (e.g., the optimized system access procedure) to improve the AGCH capacity. The sending operation includes sending an access request to the BSS, where the access request is sent when the MS is requesting to establish an uplink TBF that is triggered by a SDT or an IMT (note: the MS would send the access request124only if the BSS102is configured to perform the optimized system access procedure to improve the AGCH capacity). The second receiving operation includes receiving an immediate assignment message on the AGCH from the BSS, where the immediate assignment message includes static radio parameters and at least a portion of dynamic radio parameters. The using operation includes using the static radio parameters and the at least a portion of dynamic radio parameters when establishing the uplink TBF to transmit the SDT or IMT. This is an advantage over the prior art because the BSS by broadcasting the new SI which includes the new indicator is now able to send one immediate assignment message to multiple MSs thus improving the AGCH capacity.

In another aspect, the present invention provides a method implemented by a MS which interacts with a BSS for improving an AGCH capacity. The method comprises a first receiving step, a sending step, a second receiving step, and a using step. The first receiving step includes receiving a new SI from the base station subsystem, where the new SI includes an indicator which indicates to the MS that the BSS is configured to perform a procedure (e.g., the optimized system access procedure) to improve the AGCH capacity. The sending step includes sending an access request to the BSS, where the access request is sent when the MS is requesting to establish an uplink TBF that is triggered by a SDT or an IMT (note: the MS would send the access request124only if the BSS102is configured to perform the optimized system access procedure to improve the AGCH capacity). The second receiving step includes receiving an immediate assignment message on the AGCH from the BSS, where the immediate assignment message includes static radio parameters and at least a portion of dynamic radio parameters. The using step includes using the static radio parameters and the at least a portion of dynamic radio parameters when establishing the uplink TBF to transmit the SDT or IMT. This is an advantage over the prior art because the BSS by broadcasting the new SI which includes the new indicator is now able to send one immediate assignment message to multiple MSs thus improving the AGCH capacity.

DETAILED DESCRIPTION

Referring toFIG. 1A, there is a diagram illustrating the basic wireless signaling that occurs between a BSS102and multiple MSs1041,1042,1043,1044. . .104nto improve the capacity of the AGCH106in accordance with a first embodiment of the present invention. As shown, the BSS102broadcasts a new SI120on the BCCH122to the MSs1041,1042,1043,1044. . .104n(step1). The new SI120includes a predetermined set of packet radio resources134(i.e., static radio parameters134) which are to be used by the MSs1041,1042,1043,1044. . .104nwhenever any one of the MSs1041,1042,1043,1044. . .104nestablishes the uplink TBF128that is triggered by the SDT130aor the IMT130b(note: the new SI120indicates that the BSS120is configured to perform an optimized system access procedure to improve the AGCH capacity). The BSS102receives one or more access requests124on the RACH126from one or more MSs1041and1043(for example) which now want to transmit the SDT130aor the IMT130band are requesting to establish the uplink TBF128(step2) (note: the MS would send the access request124only if the BSS102is configured to perform the optimized system access procedure to improve the AGCH capacity). In response to receiving the access requests124, the BSS102sends the immediate assignment message132on the AGCH106to the requesting MSs1041and1043(step3). The immediate assignment message132includes at least a portion of the dynamic radio parameters136which are to be used along with the previously sent static radio parameters134by the requesting MSs1041and1043to establish the corresponding uplink TBFs128and transmit the corresponding SDT130aor IMT130b(step4). If only one MS1041(for example) sends an access request124to the BSS102during an allowed access time interval, then the BSS102could choose to send a legacy immediate assignment message which includes the complete set of dynamic radio parameters136to the individual MS1041so it can establish the uplink TBF128and transmit the SDT130aor IMT130b. Or, the BSS102could send the immediate assignment message132to the individual MS1041so it can establish the uplink TBF128and transmit the SDT130aor IMT130b.

If desired, the BSS102does not need to include all of the dynamic radio parameters in the immediate assignment message132which are needed by the MSs1041and1043to establish the uplink TBFs128. In this case, the BSS102would send a remaining portion of the dynamic radio parameters136′ in a message138on a PACCH140to the requesting MSs1041and1043which were addressed by the immediate assignment message132(step5). Furthermore, the BSS102could send additional static radio parameters134′ in the message138(or some other PACCH message if the remaining dynamic radio parameters136′ are not sent) on the PACCH140to the requesting MSs1041and1043addressed by the immediate assignment message132(step5). Then, the requesting MSs1041and1043would use the static radio parameters134(and the additional static radio parameters134′ if sent), the portion of dynamic radio parameters136(included in the immediate assignment message132), and the remaining portion of the dynamic radio parameters136′ (if sent in message138) to establish the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b(step6). In any case, this process is a marked improvement over the prior art since the traditional BSS was configured to send an immediate assignment message (which included the needed static and dynamic radio parameters) to only one MS at a time rather than being configured as in the present invention to send an immediate assignment message132to multiple MSs1041and1043(for example) at the same time which improves the capacity of the AGCH106. A more detailed discussion is provided next about the various features and advantages of the first embodiment of the present invention.

The aforementioned basic concept of the first embodiment considered here is that of allowing for a network to identify a pre-determined set of packet radio resources134(i.e. default radio resources134, static radio parameters134) that are to be used whenever a MS access request124is triggered by a SDT130aor an IMT130b. These default radio resources134are identified by including them as a new SI120which can indicate a set of one or more static radio parameters134that the network would commonly assign when using a legacy packet access procedure to assign radio resources appropriate for the MS's SDT or IMT transmissions. This new SI120has the static radio parameters134where each set of static radio parameters134includes a corresponding Radio Assignment Identity (RAID) value (referenced by the enhanced immediate assignment message132on the AGCH106) along with associated parameter values for the following Information Elements (IEs) (which can currently be included within a legacy immediate assignment message):Page ModePacket Channel DescriptionMobile AllocationStarting TimeIA Rest Octets

A network supporting the transmission of static radio parameters134as part of SI120should therefore include at least one complete set of these parameters. The MS1041,1042,1043,1044. . .104nthat receives these static radio parameters134via SI120will not need to be sent this same information on the AGCH106when attempting a system access for an SDT or IMT transmission. As such, this packet radio resource pre-allocation procedure effectively frees up AGCH capacity by modifying the immediate assignment message132to only include the dynamic radio parameters136(e.g. timing advance and TFI) (not the static radio parameters134) needed by the requesting MS1041and1043when establishing an uplink TBF128. The modified immediate assignment message132(e.g., enhanced immediate assignment (EIA) message132) allows for a greater number of MSs1041,1042,1043,1044. . .104nto be addressed by any given instance of an EIA message132when compared to a legacy immediate assignment message which can only address a single MS.

The inclusion of static radio parameters134within SI120(e.g. using SI21) indicates the BSS102supports reception of a new RACH burst that includes a new training sequence (TS) that the MS1041(for example) would send in the access request124to indicate that the SDT130aor the IMT130has triggered the access attempt. The access request124will be 11 bits long as per the legacy EGPRS Packet Channel Request message but will use different code points and as such is referred to herein as an Enhanced Packet Channel request message124which can (for example) be coded as shown in TABLE 1:

The exemplary Enhanced Packet Channel request message124shown in TABLE 1 allows for five additional code points to be defined for any additional services for which a high volume of corresponding access attempts are anticipated and therefore can be better supported using the Enhanced Packet Channel request124—Enhanced Immediate assignment message132signaling exchange described herein (i.e. new code points can be defined to support services other than SDT130aand IMT130b). In addition, this signaling scheme is not limited to being used within the context of one phase access attempts but can also be used for two access attempts. The reason that the one phase access case is indicated in TABLE 1 is that it allows for the minimum amount of control plane signaling to be used in support of SDT130aand IMT130btransmissions.

The MS1041,1042,1043,1044. . .104n(which is not a legacy MS) that supports the transmission of the enhanced packet channel request message124must of course be able to read the static radio parameters134sent as part of SI120before making such an access request124. The rate at which the MS1041,1042,1043,1044. . .104nis expected to refresh (i.e. re-read) the static radio parameters134information is nominally once every 30 seconds (i.e. as per the legacy periodicity for re-reading legacy SI). Note: The Page Mode information (proposed for inclusion in the static radio parameters134) is not expected to change often and so allowing for a nominal 30 second refresh rate for the static radio parameters134(and therefore the Page Mode) is considered to be acceptable.

It should be noted that the static radio parameters134information includes the IA Rest Octets which, as currently defined, includes USF, TFI and Request Reference information which is dynamic by its very nature. As such, either a new IA Rest Octets that excludes all dynamic information can be defined or the legacy IA Rest Octets can still be used where it is understood that the MS1041,1042,1043,1044. . .104nwill simply ignore all dynamic information regardless of what it is set to.

The BSS102's reception of an enhanced packet channel request message124on the RACH126indicates that the corresponding MS1041(for example) supports the reception of the enhanced immediate assignment message132on the AGCH106. The BSS102can therefore respond to the access request124by sending the enhanced immediate assignment message132that includes one instance of the following dynamic radio parameters136for each MS1041and1043(for example) addressed by this message:RAID corresponding to the applicable set of static radio parameters134(2 bits—allows for up to 4 sets of static radio parameters134to be included in the SI120)Echoed enhanced packet channel request code point (11 bits)—see Note 1Assigned eTFI (8 bits)—See Note 2 and 3Assigned eUSF (8 bits)—See Note 2 and 3Timing Advance (8 bits)—See Note 4FN Information (16 bits)—See Note 5

Note 1: This information overrides the 11 bit access request code point value if provided when the IA Rest Octets IE is sent as part of the static radio parameters134.

Note 2: This assumes the set of static radio parameters134indicated by RAID is only used for the MSs1041,1042,1043,1044. . .104nthat support RLC/MAC enhancements (i.e. having an RLC/MAC protocol that supports 8 bit TFI and USF values means backward compatibility will not be supported on these packet radio resources).

Note 3: It may be acceptable to leave eUSF information out of the enhanced immediate assignment message132if the BSS102, after sending the MS1041(for example) the enhanced immediate assignment message132, waits for it to move to the assigned packet radio resource and then sends it a new PACCH message138containing the eUSF information136′. In other words, if eUSF information136is missing from the enhanced immediate assignment message132then the MS1041(for example) will wait to receive the eUSF information136′ in a new RLC/MAC control message138sent on the PACCH140before it can make any uplink transmissions on the allocated packet radio resource. Similarly, the enhanced immediate assignment message132can include a legacy TFI value (5 bits) instead of an eTFI value (8 bits) in which case the MS1041(for example) will use the legacy TFI value until it receives an eTFI assignment136′ in the new RLC/MAC control message138sent on the PACCH140. Whenever PACCH signaling is used to supplement the dynamic radio parameters136sent with the enhanced immediate assignment message132then the MS1041(for example) must receive this RLC/MAC control message138before it can proceed to complete contention resolution as per the legacy one phase (or two phase) access procedure.

Note 4: It may be acceptable to leave Timing Advance information136out of the enhanced immediate assignment message132if the BSS102, after sending the MS1041(for example) the enhanced immediate assignment message132, waits for it to move to the assigned packet radio resource and then sends it a RLC/MAC control message138on the PACCH140containing the Timing Advance information136′. In other words, if Timing Advance information is missing from the enhanced immediate assignment message132, then the MS1041(for example) will wait to receive this information on the PACCH140before it can make any uplink transmissions on the allocated packet radio resource.

Note 5: With an 8 bit “RandomBits” field included in the enhanced packet channel request message124(see TABLE 1) the need for the enhanced immediate assignment message132to include any FN related info may be eliminated (i.e. for the case of access collision between two or more MSs1041,1042,1043,1044. . .104nall possible ambiguity will of course be cleaned up when contention resolution is completed but having an 8 bit “RandomBits” field can be viewed as being sufficient to ensure an acceptably low probability of having multiple MSs1041,1042,1043,1044. . .104nstill in contention after the enhanced packet channel request message124(RACH126)—enhanced immediate assignment message132(AGCH106) exchange. Alternatively, some portion of the FN (frame number) can be carried within the legacy Request Reference IE and could be included such as T1′ (seeFIG. 1B). The purpose of the legacy Request Reference information element is to provide the random access information used in the access request message124sent on the RACH126and the frame number (FN) modulo42432in which the access request124was received. In this case, the legacy Request Reference information element shown inFIG. 1Bwould be coded as follows.RA, Random Access Information (octet 2). This is an unformatted 8 bit field. Typically the contents of this field are coded the same as the CHANNEL REQUEST message shown inFIG. 1CT1′ (octet 2). The TF field is coded as the binary representation of (FN div 1326) mod 32.T3 (octet 3 and 4). The T3 field is coded as the binary representation of FN mod 51. Bit3of octet 2 is the most significant bit and bit6of octet 3 is the least significant bit.T2 (octet 4). The T2 field is coded as the binary representation of FN mod 26.
NOTE: The frame number, FN modulo42432can be calculated as 51×((T3−T2) mod 26)+T3+51×26×T1′

It should be noted that the Extended RA (5 bit field) can be included within the IA Rest Octets IE of the legacy Immediate Assignment (IA) message and has a content consisting of the 5 least significant bits of the EGPRS PACKET CHANNEL REQUEST message defined in 3GPP TS 44.060 (the contents of which are incorporated herein by reference). It is included for the case of an 11-bit access request message124since the RA field of the Request Reference IE (also included within the legacy IA message) inFIG. 1Bonly provides 8 bits of information and as such the full 11-bit access request message can only be echoed to a MS1041(for example) using supplementary information provided by the Extended RA IE.

The dynamic radio parameters136described above could be carried within the EIA Rest Octets IE of the enhanced immediate assignment message132as shown below in TABLE 2:

The sum of the length of the EIA Rest Octets IE and the L2 Pseudo Length IE equals 22 (see TABLE 2). The L2 pseudo length is the sum of lengths of all information elements present in the EIA message132except the EIA Rest Octets and L2 Pseudo Length information elements (i.e. 2 octets). This leaves 20 octets of space for the EIA Rest Octets which can be used to provide dynamic radio parameters136for a variable number of MSs1041,1042,1043,1044. . .104nas follows:

EIA Capacity Gain Case 1:

In this case all of the dynamic radio parameters136described above are included for each MS1041,1042,1043,1044. . .104naddressed by the EIA Rest Octets IE. This translates into 6 octets+5 bits per addressed MS1041,1042,1043,1044. . .104nwhich therefore allows for 3 distinct MSs to be addressed by each instance of the enhanced immediate assignment message132which results in a three-fold increase in the capacity of the AGCH106when compared to using the legacy immediate assignment message (which provides radio resources for one MS).

EIA Capacity Gain Case 2:

In this case only a subset of the dynamic radio parameters136described above are included for each MS1041,1042,1043,1044. . .104naddressed by the EIA Rest Octets IE as follows:RAID corresponding to the applicable set of SDT Radio Parameters134(2 bits)Echoed enhanced packet channel request code point (11 bits)Assigned eTFI (8 bits)

This translates into 2 octets+5 bits per addressed MS1041,1042,1043,1044. . .104nwhich allows for six distinct MSs to be addressed by each instance of the enhanced immediate assignment message132which results in a six-fold increase in the capacity of the AGCH106when compared to using the legacy immediate assignment message (which provides radio resources for one MS).

EIA Capacity Gain Case 3:

In this case only a subset of the dynamic radio parameters136described above are included for each MS1041,1042,1043,1044. . .104naddressed by the EIA Rest Octets IE as follows:RAID corresponding to the applicable set of SDT Radio Parameters134(2 bits)Echoed enhanced packet channel request code point (11 bits)Assigned Legacy TFI (5 bits)

This translates into 2 octets+2 bits per addressed MS1041,1042,1043,1044. . .104nwhich allows for eight distinct MSs to be addressed by each instance of the enhanced immediate assignment message132which results in an eight-fold increase in the capacity of the AGCH106when compared to using the legacy immediate assignment message (which provides radio resources for one MS).

EIA Capacity Gain Case 4:

In this case only a subset of the dynamic radio parameters136described above are included for each MS1041,1042,1043,1044. . .104naddressed by the EIA Rest Octets IE as follows:RAID corresponding to the applicable set of SDT Radio Parameters134(2 bits)Echoed enhanced packet channel request code point (11 bits)

A single instance of an eTFI (8 bits) is also included in the enhanced immediate assignment message132which the first addressed MS will consider as its assigned eTFI value. The 2ndaddressed MS will consider eTFI+1 as its assigned eTFI value and the 3rdaddressed MS will consider eTFI+2 as its assigned eTFI etc. . . .

This translates into 1 octet+5 bits per addressed MS+one instance of the 8 bit eTFI value which allows for 11 distinct MSs to be addressed by each instance of the enhanced immediate assignment message132which results in an eleven-fold increase in the capacity of the AGCH106when compared to using the legacy immediate assignment message (which provides radio resources for one MS).

It should be noted that following contention resolution the BSS102can choose to use PACCH signaling138to send a MS1041,1042,1043,1044. . .104none or more additional sets of static radio parameters134′. The BSS102can then refer to these static radio parameters134′ using RAID in subsequent enhanced immediate assignment messages it sends to that MS1041,1042,1043,1044. . .104n. This therefore allows the BSS102to maintain MS specific static radio parameters134′ which may be of interest for certain classes of MSs (e.g. for stationary MSs) which may allow for minimizing the amount of SI120bandwidth used to convey static radio parameters134. For example, only a single set of static radio parameters134may need to be included as part of SI120if the PACCH140is used to supplement this information as needed for specific subsets of MS1041,1042,1043,1044. . .104n.

Referring toFIG. 1D, there is a flowchart of an exemplary method100dimplemented by the BSS102which is configured to interact with multiple MSs1041,1042,1043,1044. . .104nand perform a procedure to improve the capacity of the AGCH106in accordance with the first embodiment of the present invention. The BSS102includes the processor110and the memory112that stores processor-executable instructions where the processor110interfaces with the memory112and executes the processor-executable instructions to perform method100d's steps as discussed next. At step102d, the BSS102broadcasts the new SI120on the BCCH122to the MSs1041,1042,1043,1044. . .104n. The new SI120includes a predetermined set of packet radio resources134(i.e., static radio parameters134) which are to be used by the MSs1041,1042,1043,1044. . .104nwhenever any one of the MSs1041,1042,1043,1044. . .104nestablishes the uplink TBF128that is triggered by the SDT130aor the IMT130b. At step104d, the BSS102receives one or more access requests124(within an allowed (i.e. restricted) access time interval) on the RACH126from one or more MSs1041and1043(for example) which now want to transmit the SDT130aor the IMT130band are requesting to establish the uplink TBF128. In response to receiving the access requests124, the BSS102at step206dsends the immediate assignment message132on the AGCH106for the requesting MSs1041and1043. The immediate assignment message132includes at least a portion of the dynamic radio parameters136which are to be used along with the static radio parameters134by the requesting MSs1041and1043(for example) when establishing the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b. In the event, the BSS102does not include all of the dynamic radio parameters in the immediate assignment message132sent during step106dwhich are needed by the requesting MSs1041and1043to establish the uplink TBFs128, then the BSS102at step108dcould send a remaining portion of the dynamic radio parameters136′ in a message138on a PACCH140to the requesting MSs1041and1043. If desired, the BSS102at step110dcould send additional static radio parameters134′ in the message138(or some other message if the remaining dynamic radio parameters136′ are not sent) on the PACCH140to the MSs1041and1043. Then, the MSs1041and1043would use the static radio parameters134(and the additional static radio parameters134′ if sent), the portion of dynamic radio parameters136(included in the immediate assignment message132), and the remaining portion of the dynamic radio parameters136′ (if sent in message138) to establish the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b.

Referring toFIG. 1E, there is a flowchart of an exemplary method100eimplemented by MS1041(for example) which is configured to interact with the BSS102and to improve the capacity of the AGCH106in accordance with the first embodiment of the present invention. The MS1041includes the processor116and the memory118that stores processor-executable instructions where the processor116interfaces with the memory118and executes the processor-executable instructions to perform method100e's steps as discussed next. At step102e, the MS1041receives the new SI120on the BCCH122from the BSS102. The new SI120includes a predetermined set of packet radio resources134(i.e., static radio parameters134) which are to be used by the MS1041when establishing the uplink TBF128that is triggered by the SDT130aor the IMT130b. At step104e, the MS1041sends the access request124on the RACH126when requesting to establish the uplink TBF128that is triggered by the SDT130aor the IMT130b. At step106e, the MS1041receives the immediate assignment message132on the AGCH106from the BSS102. The immediate assignment message132includes at least a portion of the dynamic radio parameters136which are to be used along with the static radio parameters134by the MS1041when establishing the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b. In the event, the BSS102does not include all of the dynamic radio parameters in the immediate assignment message132which are needed by the MS1041to establish the uplink TBFs128, then the MS1041at step108ewould receive a remaining portion of the dynamic radio parameters136′ in a message138on a PACCH140from the BSS102. Furthermore, the MS1041at step110ecould receive additional static radio parameters134′ in the message138(or some other message if the remaining dynamic radio parameters136′ are not sent) on the PACCH140from the BSS102. At step112e, the MS1041would use the static radio parameters134(and the additional static radio parameters134′ if sent), the portion of dynamic radio parameters136(included in the immediate assignment message132), and the remaining portion of the dynamic radio parameters136′ (if sent in message138) to establish the uplink TBF128to transmit the SDT130aor IMT130b.

Referring toFIG. 2A, there is a diagram illustrating the basic wireless signaling that occurs between the BSS102and the MSs1041,1042,1043,1044. . .104n(multiple MSs104shown) to improve the capacity of the AGCH106in accordance with the second embodiment of the present invention. As shown, the BSS102broadcasts a new SI120on the BCCH122to the MSs1041,1042,1043,1044. . .104n(step1). The new SI120includes an indicator302which indicates to the MSs1041,1042,1043,1044. . .104nthat the BSS102is configured to perform the optimized system access procedure to improve the capacity of the AGCH106. The content of the new SI120can be limited to providing this single indicator302if suitable static radio parameters134are provided by either the legacy SI13message or by the immediate assignment message132. The BSS102receives one or more access requests124on the RACH126from one or more MSs1041and1043(for example) which now want to transmit the SDT130aor the IMT130band are requesting to establish the uplink TBF128(step2) (note: the MS would send the access request124only if the BSS102is configured to perform the optimized system access procedure to improve the AGCH capacity). In response to receiving the access requests124, the BSS102sends the immediate assignment message132on the AGCH106to the requesting MSs1041and1043(step3). The immediate assignment message132includes a predetermined set of packet radio resources134(i.e., static radio parameters134—same as the ones described in the first embodiment), and at least a portion of the dynamic radio parameters136(same as described in the first embodiment) both of which are to be used by the requesting MSs1041and1043when establishing the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b(step4). If only one MS1041(for example) sends an access request124to the BSS102during an allowed access time interval, then the BSS102could choose to send a legacy immediate assignment message which includes the static radio parameters134and the dynamic radio parameters136to the individual MS1041so it can establish the uplink TBF128and transmit the SDT130aor IMT130b. Or, the BSS102could send the immediate assignment message132to the individual MS1041so it can establish the uplink TBF128and transmit the SDT130aor IMT130b.

If desired, the BSS102does not need to include all of the dynamic radio parameters in the immediate assignment message132which are needed by the requesting MSs1041and1043to establish the uplink TBFs128. In this case, the BSS102would send a remaining portion of the dynamic radio parameters136′ in a message138on a PACCH140to the requesting MSs1041and1043which were addressed by the immediate assignment message132(step5). Furthermore, the BSS102could send additional static radio parameters134′ in the message138(or some other message if the remaining dynamic radio parameters136′ are not sent) on the PACCH140to the requesting MSs1041and1043(step5). Then, the requesting MSs1041and1043would use the static radio parameters134(and the additional static radio parameters134′ if sent), the portion of dynamic radio parameters136(included in the immediate assignment message132), and the remaining portion of the dynamic radio parameters136′ (if sent in message138) to establish the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b(step6). In any case, this process is a marked improvement over the prior art since the traditional BSS was configured to send an immediate assignment message to only one MS at a time rather than being configured as in the present invention to send an immediate assignment message132to multiple MSs1041and1043(for example) at the same time which improves the capacity of the AGCH106.

Referring toFIG. 2B, there is a flowchart of an exemplary method200bimplemented by the BSS102which is configured to interact with multiple MSs1041,1042,1043,1044. . .104nand perform a procedure to improve the capacity of the AGCH106in accordance with the second embodiment of the present invention. The BSS102includes the processor110and the memory112that stores processor-executable instructions where the processor110interfaces with the memory112and executes the processor-executable instructions to perform method200b's steps as discussed next. At step202b, the BSS102broadcasts the new SI120on the BCCH122to the MSs1041,1042,1043,1044. . .104n. The new SI120includes an indicator302which indicates to the MSs1041,1042,1043,1044. . .104nthat the BSS102is configured to perform the procedure to improve the capacity of the AGCH106. At step204b, the BSS102receives one or more access requests124(within an allowed (i.e. restricted) access time interval) on the RACH126from one or more MSs1041and1043(for example) which now want to transmit the SDT130aor the IMT130band are requesting to establish the uplink TBF128. In response to receiving the access requests124, the BSS102at step206bsends the immediate assignment message132on the AGCH106for the requesting MSs1041and1043. The immediate assignment message132includes a predetermined set of packet radio resources134(i.e., static radio parameters134—same as the ones described in the first embodiment), and at least a portion of the dynamic radio parameters136(same as described in the first embodiment) both of which are to be used by the requesting MSs1041and1043when establishing the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b. In the event, the BSS102does not include all of the dynamic radio parameters in the immediate assignment message132which are needed by the requesting MSs1041and1043to establish the uplink TBFs128, then the BSS102at step208bwould send a remaining portion of the dynamic radio parameters136′ in a message138on a PACCH140to the requesting MSs1041and1043. If desired, the BSS102at step210bcould send additional static radio parameters134′ in the message138(or some other message if the remaining dynamic radio parameters136′ are not sent) on the PACCH140to the requesting MSs1041and1043. Then, the requesting MSs1041and1043would use the static radio parameters134(and the additional static radio parameters134′ if sent), the portion of dynamic radio parameters136(included in the immediate assignment message132), and the remaining portion of the dynamic radio parameters136′ (if sent in message138) to establish the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b.

Referring toFIG. 2C, there is a flowchart of an exemplary method200cimplemented by MS1041(for example) which is configured to interact with the BSS102and to improve the capacity of the AGCH106in accordance with the second embodiment of the present invention. The MS1041includes the processor116and the memory118that stores processor-executable instructions where the processor116interfaces with the memory118and executes the processor-executable instructions to perform method200c's steps as discussed next. At step202c, the MS1041receives the new SI120on the BCCH122from the BSS102. The new SI120includes an indicator302which indicates to the MSs1041,1042,1043,1044. . .104nthat the BSS102is configured to perform the procedure to improve the capacity of the AGCH106. At step204c, the MS1041sends the access request124on the RACH126when requesting to establish the uplink TBF128that is triggered by the SDT130aor the IMT130b. At step206c, the MS1041receives the immediate assignment message132on the AGCH106from the BSS102. The immediate assignment message132includes a predetermined set of packet radio resources134(i.e., static radio parameters134—same as the ones described in the first embodiment), and at least a portion of the dynamic radio parameters136(same as described in the first embodiment) both of which are to be used by the requesting MSs1041and1043when establishing the corresponding uplink TBFs128to transmit the corresponding SDT130aor IMT130b. In the event, the BSS102does not include all of the dynamic radio parameters in the immediate assignment message132which are needed by the requesting MS1041to establish the uplink TBFs128, then the MS1041at step208cwould receive a remaining portion of the dynamic radio parameters136′ in a message138on a PACCH140from the BSS102. Furthermore, the MS1041at step210ccould receive additional static radio parameters134′ in the message138(or some other message if the remaining dynamic radio parameters136′ are not sent) on the PACCH140from the BSS102. At step212c, the MS1041would use the static radio parameters134(and the additional static radio parameters134′ if sent), the portion of dynamic radio parameters136(included in the immediate assignment message132), and the remaining portion of the dynamic radio parameters136′ (if sent in message138) to establish the uplink TBF128to transmit the SDT130aor IMT130b.

The following detailed discussion describes various features and advantages associated with the present invention. In particular, the following detailed discussion is based on the disclosure in the aforementioned U.S. Provisional Application Serial No. 61/620,696 filed on Apr. 5, 2012. In addition, the underlined portions below highlight differences between the disclosure of U.S. Provisional Application Ser. No. 61/620,696 and an article prepared by the inventors entitled “Optimized System Access Procedure” 3GPP TSG-GERAN #54, GP-120623 and presented in Sanya, China, May 14-18, 2012. Finally, reference numerals have been added to the disclosure of U.S. Provisional Application Ser. No. 61/620,696.

Abstract

In light of increasing CCCH congestion problems anticipated as a result of M2M traffic and frequent small packet transmissions130aand130bgenerated by smart phones1041,1042,1043,1044. . .104nan enhanced procedure for PS domain triggered system access referred to as Optimized System Access Procedure (OSAP) is considered herein. The key objective of OSAP is to increase AGCH106capacity by minimizing the size of the MS specific information carried within AGCH based assignment messages132. This can be accomplished by offloading the transmission of certain radio parameters134to system information120, limiting the content136of the assignment messages132to what is strictly necessary to direct a MS1041to a packet resource and using the PACCH140of the packet resource to assign the MS1041any remaining information134′ and136′ it requires for uplink TBF128establishment. A detailed evaluation of OSAP shows that it can provide up to an eight-fold gain compared to legacy AGCH operation wherein a legacy Immediate Assignment message is assumed to assign packet resources for a single MS.

Discussion of mechanisms for improving AGCH106capacity has been ongoing for a number of GERAN meetings with possible solutions as described in references [1] and [2]. A reasonable operational example to consider that provides motivation for the OSAP feature described herein is as follows:The 51-multiframe format of a downlink CCCH could, for a given period of high system load, consist of an average of 4 PCH blocks and 5 AGCH blocks (i.e. in addition to the radio block used for BCCH Norm).For a single instance of this 51-multiframe format there would be 51 RACH bursts resulting in a RACH burst to AGCH block ratio of about 10 to 1 (reduced to about 5 to 1 when factoring in the degradation of RACH performance due to collisions inherent to slotted aloha operation) which strongly suggests the AGCH will be a bottleneck.Using IPA as a means to mitigate this imbalance results in achieving a 10 to 3 ratio (i.e. since IPA allows for up to 3 MS to be addressed by a single assignment message) but further mitigation of this imbalance is desirable if feasible (note: IPA is an alternative to OSAP and is discussed in reference [1] and later below).For DL TBF establishment when a MS is in READY STATE, the IPA feature provides no performance increase as DL TBFs will always be established using the legacy Immediate Assignment message.

The OSAP feature described herein allows for further reducing the RACH burst to AGCH block ratio as follows:Allowing for the inclusion of Mobile Allocation information134as new system information (SI)120to identify the subset of ARFCNs defined by the Cell Allocation to be used when frequency hopping is used in a given cell. The Mobile Allocation information134included as SI120can be referred to as “Static Radio Parameters” (SRP)134and would apply to packet resources assigned to mobile stations1041,1042,1043,1044. . .104nusing OSAP.Limiting the content of AGCH based assignment messages132to what is strictly necessary to direct a mobile station1041to a packet resource where it waits for a downlink PACCH message138.Sending a PACCH message138on the downlink of the assigned packet resource to provide a MS1041with all additional information134′ and136′ needed to complete the establishment of either an uplink TBF128or downlink TBF.Introducing a new AGCH message132referred to as an Enhanced Immediate Assignment (EIA) message132and a new PACCH message138referred to as an Additional TBF Information (ATI) message138.

FIG. 3Ashows an example according to the first embodiment of the present invention of how the content of 5 legacy IA messages402can be effectively distributed within (a) system information120, (b) a single EIA message132and (c) a single instance of an ATI message138(i.e. whereby a RACH burst to AGCH block ratio of 10 to 5 is realized). Additional analysis within this discussion paper shows that a single EIA message132can be used to address up to 8 different MSs1041,1042,1043,1044. . .104nthereby allowing for a 10 to 8 ratio to be realized using OSAP.

2. Optimized System Access Procedure—Overview

The SRP information134can be carried within SI120(e.g. using SI21) (according to the first embodiment of the present invention). Or, the SI120will at minimum provide an indication302(according to the second embodiment of the present invention). In any case, the SI120indicates when a serving cell supports the Optimized System Access Procedure (OSAP) wherein the corresponding BSS102is capable of receiving a new RACH burst124that involves the use of a new training sequence code (TSC). The reception of an access request message124known as an Enhanced Packet Channel Request124(EPCR) sent using this new TSC allows for introducing new OSAP specific code points in the 11-bit EPCR message as per TABLE 3 below.

The basic signaling events associated with an OSAP based system access for uplink TBF128establishment wherein a one phase access is used are shown inFIG. 3B.

3. Analysis of the Legacy Immediate Assignment Message Content

The content of the legacy Immediate Assignment message is examined below on a per information element basis to identify which information must still be included within the OSAP specific EIA message132sent on the AGCH106and which information can be sent later using one or more OSAP specific ATI message138instances sent on the PACCH140(i.e. that supplements the packet resource information provided by the OSAP specific assignment message132).

The SRP information134can be carried within SI120(e.g. using SI21) (according to the first embodiment of the present invention). Or, the SI120will at minimum provide an indication302(according to the second embodiment of the present invention). In any case, the SI120indicates that a serving cell supports OSAP based system access and Mobile Allocation information (optional). If frequency hopping is used then the Mobile Allocation information indicates the subset of RF channels belonging to the Cell Allocation used in the frequency hopping sequence.A maximum of 8 octets is needed to include SRP information134within an SI message120(i.e. a cell allocation can at most consist of 64 ARFCNs).When SRP134information or the indicator302is included within an SI message120a single instance of OSAP Mobile Allocation information is seen as being sufficient for the packet radio resources that can be assigned using the OSAP procedure.For example, the following structure could be added as a Rel-12 extension to the SI21message120.

{0 | 1 -- OSAP based system access procedure supported{ 0 -- OSAP Mobile Allocation not included as part of systeminformation| 1 < Number of Octets : bit (3) >{ < OSAP Mobile Allocation : bit (8) > } * (val(Number ofOctets)+1)}} ;
Each bit of each OSAP Mobile Allocation octet corresponds to a specific frequency in the Cell Allocation frequency list as currently described for the legacy Mobile Allocation information element.
5. Enhanced Immediate Assignment (EIA) Message132Content

This message132is formatted as shown in TABLE 5 below and is sent on the AGCH106by the network to provide mobile stations1041,1042,1043,1044. . .104nwith a minimum amount of packet resource information134(i.e. as a result of receiving this information a MS1041can only receive PACCH messages138on the packet resources assigned by the EIA message132and must therefore wait until it receives additional TBF related information134′ and136′ on the PACCH138before an uplink TBF128can be used for payload transmission or payload can be received on a downlink TBF).

The length (in octets) of all information provided by the EIA Rest Octets IE and the value provided by the L2 Pseudo Length IE has a maximum value of 22 (see TABLE 5 above). The L2 pseudo length indicates the sum of the lengths of all information elements present in the EIA message132except the EIA Rest Octets IE and the L2 Pseudo Length IE itself and as such has a value of 2. This leaves a maximum of 20 octets (160 bits) of space available for the EIA Rest Octets IE.

One instance of the EIA Rest Octets IE is included per EIA message132and consists of the fields shown in TABLE 6 below where these fields are used as follows:Page Mode (2 bits): One instance is included per EIA message132.Implicit Reject CS (1 bit): One instance is included per EIA message132. Note that this is included so that an OSAP capable MS1041,1042,1043,1044. . .104nconfigured for LAP can detect an Implicit Reject for the CS domain when it happens to read an EIA message132on the AGCH106while attempting a non-OSAP system access for the CS domain.Implicit Reject PS (1 bit): One instance is included per EIA message132. Note that this is included so that an OSAP capable MS1041,1042,1043,1044. . .104nconfigured for LAP can detect an Implicit Reject for the PS domain when it reads an EIA message132on the AGCH106that does not provide matching FN Information+Random Bits.Message Reference ID (2 bits): One instance is included per EIA message132. This information is included so that a MS1041,1042,1043,1044. . .104ncan compare the value of the Message Reference ID received in a subsequent ATI message138instance against the value received in the EIA message132and thereby verify when it has received an ATI message138instance that supplements a previously received EIA message132.Packet Channel Description (18 or 19): One instance is included per EIA message132(i.e. it is common to all MSs1041,1042,1043,1044. . .104naddressed by the EIA message132) and its content is the same as per the legacy Packet Channel Description IE (see TABLE 6 below).Mobile Allocation (1, 11, 19, 27 or 35): One instance may be included per EIA message132(i.e. when included it is common to all MS1041,1042,1043,1044. . .104naddressed by the EIA message132) and it is limited to providing 32 bits Mobile Allocation information. If more than 32 bits of Mobile Allocation information are needed or Mobile Allocation information is sent using system information120(i.e. SRP134) then this information is not included in the EIA message132.FN Information Length (2 bits): One instance is included per EIA message132and allows for 4 different lengths of FN Information to be indicated.Temporary OSAP Identity Length (2 bits): One instance is included per EIA message132and allows for 4 different lengths of Temporary OSAP Identity to be indicated.FN Information (Z bits=val(FN Information Length)+9): One instance is included per MS1041,1042,1043,1044. . .104naddressed by the EIA message132for the purpose of uplink TBF128establishment.FN Information=the binary value of ‘FN modulo X’ where FN=the TDMA frame number of the burst in which an Enhanced Packet Channel Request124was received on the RACH126by the BSS102.X can be set to reflect an acceptable probability for TDMA frame number collision. For example, for X=256 (Z=8 bits) the time between uplink bursts for which FN mod 256 has the same value is 1.18 sec (i.e. each TDMA frame=4.615 ms, 256*4.615=1.18).This means there will be some degree of uncertainty on behalf of mobile stations1041,1042,1043,1044. . .104nregarding whether or not matching ‘FN Information’ they receive in an EIA message132really reflects the specific burst in which they sent their access request message on the RACH126.The length of the MS specific FN information (Z bits) included in an EIA message132is variable allowing for operators to increase/decrease the probability of TDMA FN collision to a level they are comfortable with.Random Bits (4 bits): One instance is included per MS1041,1042,1043,1044. . .104naddressed by the EIA message132and has a corresponding instance of the FN Information field (i.e. corresponding instances of FN Information and Random Bits sent in an EIA message132are a reflection of the “Z” least significant bits of the TDMA FN and Random Bits received by the BSS102within an earlier EPCR message124).Temporary OSAP Identity (Y bits=val(Temporary OSAP Identity Length)+9): One instance is included per MS1041,1042,1043,1044. . .104naddressed by the EIA message132for the purpose of downlink TBF establishment. It allows for an HA message132to identify each mobile station1041,1042,1043,1044. . .104nbased on its specific Temporary OSAP Identity. If a MS1041,1042,1043,1044. . .104nhas not been assigned a Temporary OSAP Identity then legacy procedures are used for downlink TBF establishment.

The EIA message132is used only for the case of uplink TBF128establishment where FN Information provided for each MS1041,1042,1043,1044. . .104naddressed by the EIA message132is 9 bits long (i.e. Z=9, X=512). In this case all MS1041,1042,1043,1044. . .104nmaking access requests124within a TDMA frame where the 9 least significant bits of that TDMA frame matches the FN Information sent in the EIA message132will then look at the corresponding Random Bits field to determine if they have received a response that matches their access request124. Note that in this case the TDMA frames having the same 9 least significant bits will be a multiple of 2.36 sec apart (i.e. 512*4.615 ms=2.36 s).The EIA message132content specific to each addressed MS=FN Information (9)+Random Bits (4)+MS ID Discriminator (1)=14 bits.The EIA message132content for which a single instance is included (regardless of how many MS1041,1042,1043,1044. . .104nare addressed)=Page Mode (2)+Implicit Reject CS (1)+Implicit Reject PS (1)+Message Reference ID (2)+Packet Channel Description (19)+Mobile Allocation (1)+FN Information Length (2)+Temporary OSAP Identity Length (2)=30 bits.The maximum number of MS1041,1042,1043,1044. . .104naddressed per EIA message132=8 (i.e. 8*14+30=142).According to TABLE 6 above 10 bits of CSN.1 overhead are required for the EIA message132(1 bit to indicate no mobile allocation is included, 1 bit for each of the 8 instances of the MS Specific EIA Parameters IE included in the message and 1 bit to indicate the “direct encoding of hopping RF channel configuration” is used).The resulting EIA message132has a total length of 152 bits.

This example builds on EIA example 1 above except that it allows for 10 bits of FN Information (i.e. Z=10, X=1024) for each MS1041,1042,1043,1044. . .104naddressed by the EIA message132. In this case all MS1041,1042,1043,1044. . .104nmaking access requests124within a TDMA frame where the 10 least significant bits of that TDMA frame matches the FN Information sent in the EIA message132will then look at the corresponding Random Bits field to determine they have received a response that matches their access request124. Note that in this case the TDMA frames having the same 10 least significant bits will be a multiple of 4.72 sec apart (i.e. 1024*4.615 ms=4.72 s).The EIA message132content specific to each addressed MS=FN Information (10)+Random Bits (4)+MS ID Discriminator (1)=15 bits.The EIA message132content for which a single instance is included (regardless of how many MS are addressed)=Page Mode (2)+Implicit Reject CS (1)+Implicit Reject PS (1)+Message Reference ID (2)+Packet Channel Description (19)+Mobile Allocation (1)+FN Information Length (2)+Temporary OSAP Identity Length (2)=30 bits.The maximum number of MS1041,1042,1043,1044. . .104naddressed per EIA message132=8 (i.e. 8*15+30=150).According to TABLE 6 above 10 bits of CSN.1 overhead are required for the EIA message132(1 bit to indicate no mobile allocation is included, 1 bit for each of the 8 instances of the MS Specific EIA Parameters IE included in the message and 1 bit to indicate the “direct encoding of hopping RF channel configuration” is used).The resulting EIA message132has a total length of 160 bits.

This example builds on example 2 above except that it allows for 24 bits of Mobile Allocation information to be included within the EIA message132.The EIA message132content specific to each addressed MS=FN Information (10)+Random Bits (4)+MS ID Discriminator (1)=15 bits.The EIA message132content for which a single instance is included (regardless of how many MS are addressed)=Page Mode (2)+Implicit Reject CS (1)+Implicit Reject PS (1)+Message Reference ID (2)+Packet Channel Description (19)+Mobile Allocation (27)+FN Information Length (2)+Temporary OSAP Identity Length (2)=56 bits.The maximum number of MS1041,1042,1043,1044. . .104naddressed per EIA message132=6 (i.e. 6*15+56=146).According to TABLE 6 above 8 bits of CSN.1 overhead are required for the EIA message132(1 bit to indicate a mobile allocation is included, 1 bit for each of the 6 instances of the MS Specific EIA Parameters IE included in the message and 1 bit to indicate the “direct encoding of hopping RF channel configuration” is used).The resulting EIA message132has a total length of 154 bits
6. Additional TBF Information (ATI) Message138Content

This message138is formatted as shown in TABLE 7 below and is sent on the PACCH140by the network to provide mobile stations1041,1042,1043,1044. . .104nwith additional information134′ and136′ required for uplink TBF128or downlink TBF establishment. A set of one or more ATI message138instances can be sent by the BSS102where each instance in the set corresponds to the same EIA message132and is carried within a single PACCH block. This will minimize the amount of information any given MS1041,1042,1043,1044. . .104naddressed by a given EIA message132must receive within the EIA message132. Note that until a MS receives an ATI message138instance containing information that supplements the information it previously received in an EIA message132it can only receive on the downlink PACCH140the packet resources assigned by the EIA message132. The content of this message138consists of the following:MS Specific TBF Parameters (X bits): One instance is included per MS1041,1042,1043,1044. . .104naddressed by an ATI message138.Page Mode (2 bits): One instance is included per ATI message138.Message Reference ID (2 bits): One instance is included per ATI message138. This information is included so that a MS1041,1042,1043,1044. . .104ncan compare it to the value in the previously received EIA message132and thereby verify when it has received an ATI message138that corresponds to the EIA message132in which it detected matching FN Information and Random Bits.MS Assignment Bitmap (8 bits): One instance is included per ATI message138. This bitmap indicates which subset of MS addressed by a given EIA message132are assigned resources by a received ATI message138. Depending on the amount of MS specific information required, multiple ATI messages138corresponding to the same EIA message132can be sent. The net result is that the “Nth” MS1041,1042,1043,1044. . .104naddressed by an EIA message132will only have to correctly receive one corresponding ATI message132instance (i.e. the ATI message instance having a MS Assignment Bitmap with a “1” in bit position “N”). For example, if we assume that 5 MS1041,1042,1043,1044,1045are addressed in a given EIA message132then 2 corresponding ATI message138instances can be sent where ATI message instance 1 addresses MS1, MS2and MS3and ATI message instance 2 addresses MS4and MS5as perFIG. 3C. Thus any combination of up to 8 MSs1041,1042,1043,1044. . .104ncan be addressed in the set of ATI message138instances corresponding to the same EIA message132.

The number of MS1041,1042,1043,1044. . .104naddressed by the MS Specific TBF Parameters IE included in a given ATI message138instance can therefore be a subset of the total number of MS1041,1042,1043,1044. . .104naddressed by the MS Specific EIA Parameters IE included in the EIA Rest Octets IE (see TABLE 6) carried within the corresponding EIA message132. The ordering of MS addressed by the MS Specific TBF Parameters IE included in a given ATI message138instance will therefore be determined by the MS Assignment Bitmap IE.

ATI Example 1

ATI Example 2

ATI Example 3

In this example a two phase access assignment is considered where all MS1041,1042,1043,1044. . .104nare assigned uplink TBF128resources using the EGPRS Packet Uplink Assignment IE of TABLE 7 above:MS Specific TBF Parameters=1+EGPRS Packet Uplink Assignment (2)+{1+Access Technologies Request (0)}+Two Phase Access (1)+{1+ALPHA (4)}+GAMMA (5)+TBF_STARTING_TIME (16)+NUMBER OF RADIO BLOCKS ALLOCATED (2)+{1+P0(4)+PR_MODE (1)}+{1+PFI(7)}=47 bitsATI message138instance 1 addresses 3 MS as per FIG.3C=Page Mode (2)+Message Reference ID (2)+MS Assignment Bitmap (8)+3*(MS Specific TBF Parameters)=12+3*(47)=153 bits=1 PACCH block.ATI message138instance 2 addresses 2 MS as per FIG.3C=Page Mode (2)+Message Reference ID (2)+MS Assignment Bitmap (8)+2*(MS Specific TBF Parameters)=12+2*(47)=106 bits=1 PACCH block.
7. Downlink TBF Establishment Using OSAP Messages

Here we consider the case where a MS1041,1042,1043,1044. . .104nin Idle mode can be assigned a downlink TBF without first performing the paging procedure (i.e. the Ready timer is running and the network knows the MS location at the cell level). According to legacy operation, downlink TBF establishment is performed by sending an Immediate Assignment message that includes a Packet Downlink TBF Assignment on its paging group (if in DRX mode) or on any AGCH occurrence (if in non-DRX mode immediately following TBF release).

When considering an OSAP capable MS1041,1042,1043,1044. . .104nthe network has the option of using the EIA132and ATI138messages defined for OSAP to allocate such a MS packet resources for a downlink TBF as follows:The network must assign the OSAP capable MS1041,1042,1043,1044. . .104nan alternate identity (called a Temporary OSAP Identity) on a per cell basis that remains valid while the Ready timer is running. This requires a BSS102to have knowledge of the length of the Ready timer which can be realized in a number of ways (e.g. through the support of PFCs).The BSS102can use PACCH140signaling to assign a MS1041,1042,1043,1044. . .104na Temporary OSAP Identity (TOI) at any time while a TBF is ongoing for an OSAP capable MS1041,1042,1043,1044. . .104n.Once a MS1041,1042,1043,1044. . .104nhas been assigned a TOI then as long as it remains valid it can be included in an EIA message132that includes DL TBF related information for that MS (see the Temporary OSAP Identity field in TABLE 6).Since the use of FN Information+Random Bits (for UL TBF128establishment) or Temporary OSAP Identity (for DL TBF establishment) is indicated per instance of MS1041,1042,1043,1044. . .104naddressed by an EIA message132, any given instance of an EIA message can support any combination of MSs1041,1042,1043,1044. . .104nfor which either UL or DL TBF establishment is needed (see FIG.3D—which shows 5 MSs).The Temporary OSAP Identity can be from 9 to 12 bits in length allowing for up to a maximum of 4096 such identities to be maintained per cell.It should be noted that this mechanism for DL TBF establishment reduces the overall DL CCCH load, thus providing additional CCCH capacity for non-OSAP mobile stations.

The net benefit of having the OSAP messages also allow for DL TBF establishment is of course that a single EIA message132sent on the AGCH106can address up to 8 MS1041,1042,1043,1044. . .104nfor which DL TBF establishment is needed. An OSAP capable MS1041,1042,1043,1044. . .104nthat has been assigned a Temporary OSAP Identity will acquire SRP information134/indicator302from SI120, receive an EIA message132and a supplemental ATI message138instance to establish a DL TBF following the same steps used for UL TBF128establishment except that it is addressed using the Temporary OSAP Identity in the EIA message132(i.e. it cannot be addressed using FN Information+Random Bits since the RACH126is not used during DL TBF establishment for a MS1041,1042,1043,1044. . .104nhaving a Temporary OSAP Identity in Idle mode).

A mechanism for enhancing AGCH106capacity has been described based on introducing an optimized system access procedure (OSAP) whereby the amount of MS specific information within an assignment message132sent on the AGCH106can be minimized by using new BCCH information and PACCH140signaling to provide supplemental MS specific information. As indicated by the examples provided in section 5 above, a significant AGCH106capacity gain is possible when using OSAP (e.g. 8 mobile stations1041,1042,1043,1044. . .104ncan be addressed by a single assignment message132sent on the AGCH106). The OSAP related signaling used for UL TBF128establishment can also be used for DL TBF establishment for a MS1041,1042,1043,1044. . .104nwhose location is known at the cell level. Thereby the same AGCH106capacity gain can be achieved for any combination of UL and DL TBF establishment. Considering that the AGCH106capacity is seen as becoming increasingly problematic if the load offered by devices supporting delay tolerant applications increases significantly over the next few years, the introduction of OSAP as a new GERAN Rel-12 feature as described herein is seen as being beneficial towards minimizing the potential for the AGCH106to become a bottleneck.

REFERENCES

[1] GP-111202—Continued discussion for IPA parameters—Huawei Technologies Co., Ltd.[2] GP-111065—Usage of Higher MCSs on CCCH Downlink—Telefon AB LM Ericsson, ST-Ericsson SA[3] GP-111708—Improved AGCH Capacity using Static Radio Parameters—Telefon AB LM Ericsson, ST-Ericsson SA[4] GP-111709—Calculating the Probability of Access Collision—Telefon AB LM Ericsson, ST-Ericsson SA[5] GP-111085—Analysis on Traffic Characteristic of IM Service in China—CMCC
The references can be found at www.3GPP.org.

The following detailed discussion describes various features and advantages associated with the present invention. In particular, the following detailed discussion is based on an article prepared by the inventors which is entitled “Detailed OSAP Signalling Procedure” 3GPP TSG-GERAN #54, GP-120624 and was presented by the inventors in Sanya, China, May 14-18, 2012.

Detailed OSAP Signalling Procedures

The OSAP feature described in a companion discussion paper (the aforementioned GP-120623) involves the introduction of new signaling procedures for more efficiently establishing both uplink and downlink TBFs. The detailed signaling procedures associated with the OSAP feature used for establishing uplink and downlink TBFs are examined in greater detail herein where it can be seen that this signalling essentially consists of a combination of new signaling combined with legacy signaling as follows:New BCCH information120that indicates the OSAP feature is supported by the network and which provides information about the packet data resources that can be assigned using OSAP based signaling.A new RACH message124that allows a BSS102to uniquely determine that a MS1041,1042,1043,1044. . .104nis requesting OSAP based signaling for uplink TBF128establishment.New AGCH and PACCH signaling132and138supporting the establishment of uplink and downlink TBFs used for uplink and downlink user data transmission (e.g.130aand130bfor the case of uplink data transmission).The legacy one phase and two phase contention resolution procedure for uplink TBF128establishment.Legacy TBF management and release procedures for uplink and downlink TBFs established using OSAP based signaling.
2. OSAP—Detailed Operation for UL TBF128Establishment

A serving cell that supports OSAP based signaling is managed by a corresponding BSS102that is capable of receiving a new 11-bit RACH message124consisting of an access burst that involves the use of a new training sequence code (TSC). Upon reading all OSAP related system information, an OSAP capable MS1041,1042,1043,1044. . .104nwill use this new TSC along with the signaling procedures shown inFIG. 4A(OSAP Signalling Procedures for UL TBF Establishment-Part1) andFIG. 4B(OSAP Signalling Procedures for UL TBF Establishment-Part2) below whenever it has uplink payload to send for the PS domain.The structures within the box labeled with the numeral “A” inFIGS. 4A-4Bindicate the use of new procedures and timers whereas the remaining structures indicate the use of legacy procedure and timers.The OSAP based signalling described below allows for both one phase and two phase system access procedures and corresponding contention resolution as per legacy operation.The code points supported by the new 11-bit RACH message124allow for indicating the same basic types of access requests as can be requested using legacy RACH messages (i.e. “one phase access”, “two phase access”, “signaling” and “single block packet access”).OSAP based signaling described below allows a BSS102to respond to a new RACH burst124by directing a MS1041,1042,1043,1044. . .104nto use either a one phase or two phase system access according to the flexibility supported by legacy operation.

1) An OSAP capable MS1041,1042,1043,1044. . .104nreads OSAP specific system information120once every 30 seconds as per the legacy SI refresh rate and then enters Idle mode.

2) All PS domain access attempts triggered by a MS1041,1042,1043,1044. . .104ncapable of OSAP are subject to using OSAP procedures whereas all CS domain access attempts triggered by such a MS1041,1042,1043,1044. . .104nwill be managed using legacy CS domain related procedures. An OSAP capable MS1041,1042,1043,1044. . .104nattempting a PS domain access therefore schedules and starts sending new RACH bursts referred to as Enhanced Packet Channel Request (EPCR) messages124which support 11 bits of payload space and a training sequence code (TSC) that allows a BSS102to uniquely detect reception of an EPCR message124.

The code points supported by the EPCR message124allow for a MS1041,1042,1043,1044. . .104nto indicate “one phase access”, “two phase access”, “signaling” and “single block packet access” as per PS domain related code points supported by the legacy EGPRS Packet Channel Request message (see TABLE 8).

3) After starting the access procedure by transmitting an EPCR message124the MS1041,1042,1043,1044. . .104nstarts looking for an Enhanced Immediate Assignment (EIA) message132with matching “FN Information” and “Random Bits”. T3146(legacy) is only started after the maximum number of EPCR messages124have been transmitted.

4) Upon receiving an Enhanced Immediate Assignment (EIA) message132with matching “FN Information” and “Random Bits” (carried within the MS Specific EIA Parameters IE) the MS1041,1042,1043,1044. . .104nstops T3146(if running), starts T3226(new), moves to the indicated PDCH resources and monitors the downlink PACCH140for a matching Additional TBF Information (ATI) message138. Note that this means a BSS102must respond to an EPCR message124by sending an EIA message132since a MS1041,1042,1043,1044. . .104nperforming an OSAP based system access will only consider EIA messages132as potentially containing a matching response.

5) Upon receiving an ATI message138instance the MS1041,1042,1043,1044. . .104nreads the “MS Assignment Bitmap” therein to determine if it is addressed by that ATI message instance. In other words, if it considered the Nth instance of information carried within the MS Specific EIA Parameters IE of the EIA message132to contain matching information then it checks to see if the Nth bit of this bitmap is set to “1”. If the Nth bit is set to “1” then the MS1041,1042,1043,1044. . .104nconcludes that the corresponding instance of the MS Specific TBF Parameters IE in the received ATI message138provides it with all remaining information134′ and136′ needed for uplink TBF128establishment including whether or not it is to proceed using the one phase access or the two phase access procedure (seeFIG. 4B).

A small Message Reference ID field (2 bits long) is present within both the EIA message132and ATI message138so that a MS1041,1042,1043,1044. . .104ncan precisely associate a received ATI message138instance to the specific EIA message132that has the same Message ID value:Note that the EIA message132will not include any TFI information (as it will instead be included in the ATI message138) and as such a MS1041,1042,1043,1044. . .104nassumes that if it received a match in the Nth instance of the MS specific information in an EIA message132then it is to use the Nth instance of the MS specific information in the ATI message138corresponding to that EIA message132.Since an ATI message138instance may potentially be missed by a mobile station1041,1042,1043,1044. . .104n(i.e. even though it is sent using CS-1 coding) a BSS102may choose to make limited pre-emptive re-transmissions of these messages.During times of heavy system access load a BSS102may need to send different sets of one or more ATI message138instances (i.e. each set of one or more ATI message138instances is unique in that it addresses the specific group of mobile stations1041,1042,1043,1044. . .104naddressed by its corresponding EIA message132) in relatively quick succession on the PACCH140of a specific packet resource while also making use of pre-emptive ATI message re-transmissions.As such, to avoid the potential for a MS1041,1042,1043,1044. . .104nto incorrectly associate an ATI message138instance with a previously received EIA message132(and thereby apply incorrect additional TBF information), the introduction of a two bit Message Reference ID field in both the EIA and ATI messages132and138is seen as being sufficient.

6) If T3146expires prior to receiving a matching EIA message132or T3226expires before receiving a matching ATI message138then the MS1041,1042,1043,1044. . .104naborts the packet access attempt and returns to Idle mode.

7) If the ATI message138indicates a one phase access is to be used the MS1041,1042,1043,1044. . .104nstops T3226, starts T3164and waits for the first instance of its assigned USF. Upon receiving the first instance of its assigned USF, the MS1041,1042,1043,1044. . .104nstops T3164, sends its first RLC data block and proceeds with one phase access contention resolution according to legacy procedures. Note that even if a MS1041,1042,1043,1044. . .104nindicates a one phase within an EPCR message124(see TABLE 8) the BSS102can still send an ATI message138that forces the MS1041,1042,1043,1044. . .104nto perform a two phase access (see step10below).

8) If contention resolution is successful the MS1041,1042,1043,1044. . .104ncompletes the transmission of its user data (LLC PDU) according to legacy operation. After completing the transmission of its user data the uplink TBF128is released according to legacy procedures.

9) If T3164expires before the MS1041,1042,1043,1044. . .104nreceives the first instance of its assigned USF or it experiences unsuccessful one phase contention resolution it may either retry the packet access or abort the uplink TBF128as per legacy procedures.

10) If the ATI message138indicates a two phase access is to be used then the MS1041,1042,1043,1044. . .104nstops T3226, sends a PRR, starts T3168and waits for a PUA in response to the PRR. Upon receiving the PUA the MS1041,1042,1043,1044. . .104nproceeds with two phase contention resolution according to legacy procedures.

Note that, similar to legacy operation, if the establishment cause in the EPCR message124indicates a request for a one phase packet access or signaling the network may send an ATI message138that grants either a one phase access or a two phase access. If a Multi Block allocation is granted by the ATI message138it forces the mobile station1041,1042,1043,1044. . .104nto perform a two phase access.

11) If contention resolution is successful the MS1041,1042,1043,1044. . .104nstops13168, starts T3164and waits for the first instance of its assigned USF. Upon receiving the first instance of its assigned USF then the MS1041,1042,1043,1044. . .104nstops T3164and begins transmitting its user data (LLC PDU) according to legacy operation. After completing the transmission of its user data the TBF128is released according to legacy procedures.

12) If T3168expires before the MS1041,1042,1043,1044. . .104nreceives a PUA in response to the PRR or T3164expires before the MS1041,1042,1043,1044. . .104nreceives the first instance of its assigned USF or it experiences unsuccessful two phase contention resolution then the MS1041,1042,1043,1044. . .104nmay either retry the packet access or abort the uplink TBF128as per legacy procedures.

The scenario addressed is where an OSAP capable MS1041,1042,1043,1044. . .104nis in Idle mode and can be assigned a downlink TBF without first performing the paging procedure because its corresponding Ready timer is running and the network therefore knows the MS location at the cell level. In this case downlink TBF establishment is performed as shown inFIG. 4C(OSAP Signalling Procedures for DL TBF Establishment).

1) During an ongoing TBF the BSS102may at any time use PACCH140signaling assign a Temporary OSAP Identity (TOI) to an OSAP capable MS1041,1042,1043,1044. . .104n. The assigned TOI remains valid for as long as the Ready timer is running and therefore requires a BSS102to have knowledge of the length of the Ready timer (e.g. this can be realized if PFC procedures are supported by the network).

2) Upon receiving downlink payload (i.e. LLC PDUs) for a MS1041,1042,1043,1044. . .104nin Idle mode having a valid TOI the BSS102initiates downlink TBF establishment by sending an EIA message132that includes the TOI of that MS (i.e. instead of FN Information+Random Bits):If the non-DRX mode feature is not supported (i.e. at TBF release the MS1041,1042,1043,1044. . .104nimmediately enters the DRX mode) the BSS102sends the EIA message132on the CCCH of the corresponding serving cell using any of the radio blocks defined by the paging group of that MS as defined in 3GPP TS 45.002 (the contents of which are incorporated herein by reference).If the non-DRX mode feature is supported (i.e. at TBF release the MS1041,1042,1043,1044. . .104nimmediately enters the non-DRX mode for a period of time determined by the non-DRX timer) and the BSS102determines that the MS1041,1042,1043,1044. . .104nis in the non-DRX mode it may send the EIA message132on the CCCH of the corresponding serving cell using any non-BCCH blocks. Otherwise, it sends the EIA message132on the CCCH of the corresponding serving cell using any of the radio blocks defined by the paging group of that MS).

3) Upon receiving an Enhanced Immediate Assignment (EIA) message132with matching TOT (carried within the MS Specific EIA Parameters IE) the MS1041,1042,1043,1044. . .104nstops the non-DRX timer (if running), starts T3226(new), moves to the indicated PDCH resources and monitors the downlink PACCH140for a matching Additional TBF Information (ATI) message138.

4) Upon receiving an ATI message138instance the MS1041,1042,1043,1044. . .104nreads the “MS Assignment Bitmap” therein to determine if it is addressed by that ATI message instance. In other words, if it considered the Nth instance of information carried within the MS Specific EIA Parameters IE of the EIA message132to contain matching information then it checks to see if the Nth bit of this bitmap is set to “1”. If the Nth bit is set to “1” then the MS1041,1042,1043,1044. . .104nconcludes that the corresponding instance of the MS Specific TBF Parameters IE in the received ATI message138provides it with all remaining information needed for downlink TBF establishment.

5) If T3226expires before receiving a matching ATI message138then the MS1041,1042,1043,1044. . .104naborts the downlink TBF establishment attempt and returns to Idle mode.

The detailed operation of the OSAP procedure as described above effectively involves the distribution of uplink TBF128specific information over the BCCH122, AGCH106and PACCH140(as compared to just the AGCH for legacy operation). This allows the MS specific portion of this distributed information sent on the AGCH106to be significantly reduced compared to legacy operation and an AGCH gain is thereby realized in that the number of MS1041,1042,1043,1044. . .104naddressed per OSAP specific AGCH assignment message132can be significantly increased compared to legacy AGCH assignment messages. Considering that AGCH106capacity is seen as becoming increasingly more problematic as system access load increases (e.g. due to the increased traffic load by MTC as well as increased use of instant messaging type applications) the introduction of OSAP as a new GERAN Rel-12 feature as described herein is seen as providing an essential AGCH capacity improvement.

The following discussion describes the various advantages that the OSAP procedure of the present invention has over the IPA procedure that has been presented by Huawei Technologies Co., Ltd. The first detailed discussion is based on an article prepared by the inventors which is entitled “IPA Analysis for Uplink Assignments” 3GPP TSG-GERAN #55, GP-120979 and was presented in Vienna, Austria, Aug. 27-31, 2012. And, the second detailed discussion is based on an article prepared by the inventors which is entitled “IPA Analysis for Downlink Assignments” 3GPP TSG-GERAN #55, GP-120980 and was presented in Vienna, Austria, Aug. 27-31, 2012.

IPA Analysis for Uplink Assignments (see GP-120979)

The IPA feature was included in the Rel-11 GERAN specifications in light of operator networks that experience a high CCCH load and thus have typically made use of Multiple CCCH (MCCCH) as a means for dealing with this load. However, when considering IPA as an alternative mechanism for alleviating high CCCH load for the case of uplink TBF establishment, additional consideration must be given to network scenarios with high load where the use of one phase system access is prioritized.

It is shown in this paper that for the case of one phase access IPA will at best be able to support the assignment of two uplink TBFs, because IPA must provide more MS specific information than it does for the case of a two phase access. As such, the IPA capabilities as indicated by reference [1] have been further considered resulting in the following findings:For the one phase access case, a maximum of two MS can be addressed within an IPA message regardless if hopping is used or not (as opposed to 3 MS being addressable for the non-hopping case as suggested by reference [1]).For the one or two phase access cases where the Direct Encoding option is used there is no gain as only one MS can be addressed within an IPA message (this is not discussed in reference [1]).
2. IPA Message Space Analysis

Considering the 19 octet payload space limitation of the “IPA Rest Octets IE” (see Annex A.1 below) and analyzing the proposed content for this IE for the case of uplink TBF assignments where the BCCH carrier is not used, the following should be noted:

2.1 One Phase Access

A best case scenario for IPA message space utilization for the one phase access case (the IPA Uplink Assignment struct is used) when no frequency hopping is used in which case the Frequency Parameters struct provides information on a ARFCN (see highlighted text in Annex A.2 below). When uplink TBF resources are assigned for this best case scenario we get the following bit space utilization:Total bits=1+[N*(1+43)+1]+3+1+(3+2+10)+1+1 where N=the number of MS addressed by the IPA message→maximum value for N=2 (total bits=1+[2*44+1]+4+15+2=111 bits).This means only 41 bits of payload space will remain according to the 152 bit limit which is not enough to support uplink resource assignments for a 3rd mobile station.A worst case scenario for IPA message space utilization for the one phase access case when frequency hopping is used in which case the Frequency Parameters struct can be provided using Direct encoding 2 information (see magenta shaded text in Annex A.2 below). When uplink TBF resources are assigned for this worst case scenario we get the following bit space utilization:Total bits=1+[N*(1+43)+1]+3+1+(3+2+6+6+4+64)+1+1 where N=the number of MS addressed by the IPA message→maximum value for N=1 (total bits=1+[1*44+1]+4+85+2=137 bits).This means only 15 bits of payload space will remain according to the 152 bit limit which is not enough to support uplink resource assignments for a 2nd mobile station.
2.2 Two Phase AccessA best case scenario for IPA message space utilization for the two phase access case (the IPA Single Block Uplink Assignment struct is used) is where the Frequency Parameters struct provides ARFCN information (see highlighted text in Annex A.2 below). When uplink TBF resources are assigned for this best case scenario we get the following bit space utilization:Total bits=1+1+[N (1+36)+1]+3+1+(3+2+10) where N=the number of MS addressed by the IPA message→maximum value for N=3 (total bits=2+[3*37+1]+4+15=133 bits).This means only 19 bits of payload space will remain according to the 152 bit limit which is not enough to support uplink resource assignments for a 4th mobile station.A worst case scenario for IPA message space utilization for the two phase access case is where the Frequency Parameters struct provides the Direct encoding 2 information (see bold text in Annex A.2 below). When uplink TBF resources are assigned for this worst case scenario we get the following bit space utilization:Total bits=1+1+[N*(1+36)+1]+3+1+(3+2+6+6+4+64) where N=the number of MS addressed by the IPA message→maximum value for N=1 (total bits=2+[1*37+1]+4+85=129 bits).This means only 23 bits of payload space will remain according to the 152 bit limit which is not enough to support uplink resource assignments for a 2nd mobile station.
2.3 Baseband Frequency Hopping UsedA common deployment scenario is where baseband frequency hopping is used and the BCCH frequency is within the hopping set in which case the Frequency Parameters IE needs to be included since MAIO and HSN type information will be needed by a mobile station. For this scenario, when the Frequency Parameters IE provides this information using either the Direct Encoding 1 or Direct Encoding 2 option the worst case scenarios identified in 2.1 and 2.2 above will apply. However, when the Frequency Parameters IE provides this information using the Indirect Encoding option the best case scenarios identified in 2.1 and 2.2 above will apply.
2.4 Baseband Frequency Hopping not UsedAnother deployment scenario may be that where baseband hopping is not used and the BCCH carrier is not preferred for PS resource allocations (e.g. due to the reduced efficiency of PDCH resource utilization resulting from non-contiguous PDCHs when MCCCH is used on the BCCH carrier or when SDCCHs are allocated on the BCCH carrier). This will require ARFCN information to be provided by the Frequency Parameters IE which corresponds to the best case scenarios identified in 2.1 and 2.2 above.
2.5 Implicit Reject InformationThough not currently specified, the “IPA Rest Octets IE” needs to include a bit for indicating “Implicit Reject CS” and a bit for indicating “Implicit Reject PS” since the IPA message can be sent on the AGCH and should therefore be able to convey implicit reject information for IPA capable mobile stations. Adding these 2 bits will make the IPA Rest Octets bit shortage problem even worse.
3. Conclusion

When considering the case of system operation where IPA is used as an alternative mechanism for alleviating high CCCH load, even if the best case scenario of IPA message space utilization is considered, IPA will only be able to support the assignment of uplink TBFs for a maximum of 2 mobile stations when the use of one phase access is prioritized. As such, the use of the IPA feature may in practice only provide a very limited improvement in AGCH signalling capacity regarding uplink TBF assignments which may not be sufficient for longer term AGCH loading scenarios.

REFERENCES

The reference can be found at www.3GPP.org.

9.1.18a Immediate Packet Assignment

This message is sent on the CCCH by the network to multiple mobile stations in idle mode to assign either an uplink or a downlink packet data channel configuration in the cell. See table 9.

The L2 pseudo length of this message is the sum of lengths of all information elements present in the message except the IPA Rest Octets and L2 Pseudo Length information elements.NOTE: The network should take into account limitations of certain mobile stations to understand IMMEDIATE PACKET ASSIGNMENT message as these mobile stations may not be able to decode the Page Mode information element.Message type: IMMEDIATE PACKET ASSIGNMENTSignificance: dualDirection: network to mobile station

The IPA Rest Octets information element contains spare bits and possibly at least one of the IPA Uplink Assignment struct, the IPA Downlink Assignment struct, and the IPA Single Block Uplink Assignment struct.

The IPA Rest Octets information element is coded according to the syntax specified below and described in table 10.

The IPA Rest Octets information element is a type5information element with 0-19 octets length.

The IPA feature was included in the Rel-11 GERAN specifications in light of operator networks that experience a high CCCH load and thus have typically made use of Multiple CCCH (MCCCH) as a means for dealing with this load. However, when considering IPA as an alternative mechanism for alleviating high CCCH load for the case of downlink TBF establishment, IPA will at best be able to support the assignment of downlink TBFs for 2 mobile stations using the “IPA Downlink Assignment struct”. As such, the IPA capabilities as indicated by reference [1] have been further considered resulting in the following findings:When the Direct Encoding option is used for IPA there is no gain as only one MS can be addressed within an IPA message (this is not discussed by reference [1]).
2. IPA Message Space Analysis

Considering the 19 octet payload space limitation of the “IPA Rest Octets IE” (see Annex A.1 below) and analyzing the proposed content for this IE for the case of downlink TBF assignments where the BCCH carrier is not used, the following should be noted:A best case scenario for IPA message space utilization is where the Frequency Parameters strict provides ARFCN information (see highlighted text in Annex A.2 below). When downlink TBF resources are assigned for this best case scenario we get the following bit space utilization:Total bits=1+[N*(1+49)+1]+1+1+3+1+(3+2+10)+1 where N=the number of MS addressed by the IPA message→maximum value for N=2 (total bits=1+[2*50+1]+6+15+1=124 bits).This means only 28 bits of payload space will remain according to the 152 bit limit which is not enough to support downlink resource assignments for a 3rd mobile station.A worst case scenario for IPA message space utilization is where the Frequency Parameters struct provides the Direct encoding 2 information (see bold text in Annex A.2 below). When downlink TBF resources are assigned for this worst case scenario (64 bits of Mobile Allocation information provided) we get the following bit space utilization:Total bits=1+[N*(1+49)+1]+1+1+3+1+(3+2+6+6+4+64)+1 where N=the number of MS addressed by the IPA message→maximum value for N=1 (total bits=1+[1*50+1]+6+85+1=144 bits).This means only 8 bits of payload space will remain according to the 152 bit limit which is not enough to support downlink resource assignments for a 2nd mobile station.It should also be noted that the Direct encoding 2 struct allows for more than 64 bits of Mobile Allocation information in which case an IPA message will not even be able to assign downlink TBF resources for even 1 mobile station.A common deployment scenario is where baseband frequency hopping is used and the BCCH frequency is within the hopping set in which case the Frequency Parameters IE needs to be included since MAIO and HSN type information will be needed by a mobile station. For this scenario, when the Frequency Parameters IE provides this information using either the Direct Encoding 1 or Direct Encoding 2 option the worst case scenario above will apply. However, when the Frequency Parameters IE provides this information using the Indirect Encoding option the best case scenario above will apply.Another deployment scenario may be that where baseband hopping is not used and the BCCH carrier is not preferred for PS resource allocations (e.g. due to the reduced efficiency of PDCH resource utilization resulting from non-contiguous PDCHs when MCCCH is used on the BCCH carrier or when SDCCHs are allocated on the BCCH carrier). This will require ARFCN information to be provided by the Frequency Parameters IE which corresponds to the best case scenario above.Though not currently specified, the “IPA Rest Octets IE” needs to include a bit for indicating “Implicit Reject CS” and a bit for indicating “Implicit Reject PS” since the IPA message can be sent on the AGCH and should therefore be able to convey implicit reject information for IPA capable mobile stations. Adding these 2 bits will make the IPA Rest Octets bit shortage problem even worse.
3. Conclusion

When considering the case of system operation where IPA is used as an alternative mechanism for alleviating high CCCH load, even if the best case scenario of IPA message space utilization is considered IPA will only be able to support the assignment of downlink TBFs for a maximum of 2 mobile stations. As such, the use of the IPA feature may in practice only provide a very limited improvement in AGCH signalling capacity regarding uplink TBF assignments which may not be sufficient for longer term AGCH loading scenarios.

REFERENCE

The reference can be found at www.3GPP.org.

9.1.18a Immediate Packet Assignment

This message is sent on the CCCH by the network to multiple mobile stations in idle mode to assign either an uplink or a downlink packet data channel configuration in the cell. See table 11.

The L2 pseudo length of this message is the sum of lengths of all information elements present in the message except the IPA Rest Octets and L2 Pseudo Length information elements.NOTE: The network should take into account limitations of certain mobile stations to understand IMMEDIATE PACKET ASSIGNMENT message as these mobile stations may not be able to decode the Page Mode information element.Message type: IMMEDIATE PACKET ASSIGNMENTSignificance: dualDirection: network to mobile station

The IPA Rest Octets information element contains spare bits and possibly at least one of the IPA Uplink Assignment struct, the IPA Downlink Assignment strut, and the IPA Single Block Uplink Assignment struct.

The IPA Rest Octets information element is coded according to the syntax specified below and described in table 12.

The IPA Rest Octets information element is a type5information element with 0-19 octets length.

Although multiple embodiments of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that the invention is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications and substitutions without departing from the present invention that as has been set forth and defined within the following claims.