Abstract:
A CDMA telecommunication system utilizes a plurality of protocol layers including a physical layer and a medium access control (MAC) layer such that the MAC layer provides data to the physical layer via plurality of transport channels (TrCHs). Each TrCH is associated with a set of logical channels. The physical layer receives blocks of data for transport such that the transport blocks (TBs) includes a MAC header and logical channel data for a selected logical channel associated with a given TrCH. Each TB has one of a selected limited finite number of TB bit sizes. The logical channel data for each TB has a bit size evenly divisible by a selected integer N greater than three (3). The MAC header for each TB has a bit size such that the MAC header bit size plus the logical channel data bit size equals one of the TB bit sizes. A fixed MAC header bit size is associated with each logical channel for a given TrCH and is selected such that each fixed MAC header bit size equals M modulo N where M is an integer greater than 0 and less than N, i.e. each MAC header for a given TrCH has a bit offset equal to M.

Description:
This application claims priority from U.S. Provisional Application No. 60/176,150, filed Jan. 14, 2000. 
    
    
     The present invention relates to wireless communication systems and, in particular, the selective sizing of data blocks for wireless transport of data in an efficient manner. 
     BACKGROUND OF THE INVENTION 
     Radio interfaces such as those proposed by the 3 rd  Generation Partnership Project (3G) use Transport Channels (TrCHs) for transfer of user data and signaling between User Equipment (UE), such as a Mobile Terminal (MT), and a Base Station (BS) or other device within node of a communication network. In 3G Time Division Duplex (TDD), TrCHs are a composite of one or more physical channels defined by mutually exclusive physical resources. TrCH data is transferred in sequential groups of Transport Blocks (TBs) defined as Transport Block Sets (TBSs). Each TBS is transmitted in a given Transmission Time Interval (TTI). User Equipment (UE) and Base Station (BS) physical reception of TrCHs require knowledge of Transport Block (TB) sizes. 
     For each TrCH, a Transport Format Set (TFS) is specified containing Transport Formats (TFs). Each TF, defines a TBS composed of a specified number of TBs where each TB preferably has the same size within a given TBS. Thus, a finite number of potential TB sizes are defined with respect to each TrCH. 
     Radio Resource Control (RRC) signaling is required between the BS and UE to define the attributes of each established TrCH, including a list of potential TB sizes. Signaling over the radio interface introduces system overhead, which reduces the physical resources available for user data transmission. Therefore, it is important to minimize RRC signaling and the number of potential TrCH TB sizes respectively. 
     All data transferred by specific TrCHs must fit into the TB sizes specified for the TFS of a particular TrCH. However, variable size data blocks exist that can not be predicted, for Radio Access Network (RAN) and Core Network (CN) signaling data, as well as Non-Real Time (NRT) user data transmissions. 
     To allow for the transfer of variable size data blocks, a Radio Link Control (RLC) provides a segmentation and re-assembly multiplexing function and a padding function. The segmentation and re-assembly multiplexing function reduces the size prior to transmission RLC and is used when the transferred data block is larger then the maximum allowed TB size. The padding function increases the data block or segmented data block size by padding with extra bits to fit a TB size. 
     Segmentation and re-assembly of data over more than one TTI is permitted for some, but not all, types of data. In 3G, it is not permitted, for example, for Common Control Channel (CCCH) logical data. Thus, the payload requirements for a TrCH carrying logical CCCH data are inherently restricted. 
     The RLC processing results in blocks of data are called Protocol Data Units (PDUs). A certain amount of each RLC PDU is required for control information. Using a relatively small RLC PDU results in a lower transfer data to control information ratio consequently resulting in a less efficient use of radio resources. The RLC padding function is used when the transferred data block is not equal to any of the allowed TB sizes. Likewise, the greater the difference between the transferred data block size and the next larger allowed TB size results in lowering the transfer data to used physical resources ratio consequently resulting in a less efficient use of radio resources. Therefore, it is important to maximize the number of potential TB sizes. 
     Lowering the number of TB sizes reduces RRC signaling overhead and increases radio interface efficiency. Increasing the number of TB sizes reduces RLC overhead and increases radio interface efficiency. It is therefore important to make the best use of the specified TB sizes for each TrCH. 
     TB sizes are the sum of the RLC PDU size and a Medium Access Control (MAC) header size. The MAC header size is dependent of the class of traffic, which is indicated by the Logical Channel type. A Target Channel Type Field (TCTF) is provided in the MAC header to indicate to which logical channel a TB is assigned. A TrCH can support multiple logical channel types. This means that the finite number of allowed TB sizes must support several MAC header sizes. 
     For RAN and CN signaling data and NRT user data, the RLC generates octet aligned (8 bit quantities) PDU sizes. Thus, the RLC PDUs are defined as groups of a selected number of octets, such that the RLC PDU bit size is always evenly divided by eight, i.e. the RLC PDU bit size always equals 0 modulo 8. This characteristic is maintained even when padding is required. 
     Applicant has recognized that, if MAC header sizes for different Logical Channel types have mutually exclusive bit offsets, TB sizes can not be generically used for all transmissions. TB sizes have to be defined for specific MAC headers and logical channels respectively. This increases signaling overhead and reduces RLC PDU size options, which results in less efficient use of radio resources. 
     Specifying octet aligned MAC header sizes as is currently done in some 3 rd  generation systems allows for some sharing of TB sizes between different Logical Channel types, but also increases MAC signaling overhead since the MAC header size must be at least 8 bits in such situations. In 3 rd  generation TDD mode, certain TrCH and Logical Channel combinations have very limited transfer block sizes and increasing MAC overhead should be avoided. Therefore, in TDD, TB size definitions are specific to Logical Channel specific MAC header bit offsets, and as described, reduces overall radio resource efficiency. 
     Applicant has recognized that without common MAC header bit offsets, it is not possible for MT down-link and BS up-link transmissions to octet align received frames in a physical layer since the bit offset is based on the logical channel type which cannot be known while at the physical layer. Therefore, TB&#39;s have to be transferred to layer  2  for logical channel determination before bit shifting can occur. This means that considerable processing overhead is introduced for these TrCH&#39;s. Applicant has recognized that with TrCH specific bit aligned MAC headers, bit shifting is known at the physical layer and no additional processing overhead is introduced. 
     SUMMARY OF THE INVENTION 
     A CDMA telecommunication system utilizes a plurality of protocol layers including a physical layer and a medium access control (MAC) layer such that the MAC layer provides data to the physical layer via plurality of transport channels (TrCHs). Each transport channel (TrCH) is associated with a set of logical channels for transporting logical channel data within transport channel data. At least one TrCH is associated with a set of logical channels having at least two logical channels of different types. 
     The physical layer receives blocks of data for transport such that the transport blocks (TBs) of data includes of a MAC header and logical channel data for one of the TrCHs. Each TB transports data for a given TrCH such that the logical channel data includes data associated with a selected logical channel from the set of logical channels associated with the given TrCH. Each TB has one of a selected limited finite number of TB bit sizes. The logical channel data for each TB has a bit size evenly divisible by a selected integer N greater than three (3). N is preferably eight (8) so that the logical data is in the form of an RLC PDU defined in terms of octets of data bits. Preferably the data manipulation and formatting is performed by one or more computer processors. 
     The MAC header for each TB includes data identifying the selected logical channel and has a bit size such that the MAC header bit size plus the logical channel data bit size equals one of the TB bit sizes. The MAC header bit size is fixed for TBs transporting data for the same TrCH and same selected logical channel, but may be different from the MAC header bit size for TBs transporting data for either a different TrCH or a different selected logical channel. 
     Preferably, for TrCHs associated with a set of multiple types of logical channels, a fixed MAC header bit size is associated with each logical channel within the set of logical channels and is selected such that each fixed MAC header bit size equals M modulo N where M is an integer greater than 0 and less than N. This results in a MAC header bit offset of M which is the same for all MAC headers associated with a given TrCH. This allows for a MAC header to be smaller than N in size. Thus, when N is 8, such as for octet aligned RLC PDUs, a MAC header can be smaller than one octet of data. 
     Preferably, each MAC header has a data field for data identifying the selected type of logical channel associated with the logical channel data. A bit size of that data field is preferably selected to determine the modulo N bit size of the MAC header, i.e. the MAC header bit offset. A shortest data field bit size is preferably provided for the data field of the MAC header of one or more logical channels of the set associated with the respective TrCH such that the logical channels designated by the shortest data field size are collectively more frequently used with the respective TrCH than any other logical channel within the associate set of logical channels. Alternatively, the shortest data field bit size may be associated with the most restricted TrCH logical channel combination payload requirement. 
     Preferably, the TrCHs includes a forward access channel (FACH) associated with a set of logical channels including a dedicated traffic channel (DTCH), a dedicated control channel (DCCH), a shared channel control channel (SHCCH), a common control channel (CCCH) and a common traffic channel (CTCH), and a random access channel (RACH) associated with a set of logical channels including the DTCH, the DCCH, the SHCCH and the CCCH. In such case, each MAC header preferably has a Target Channel Type Field (TCTF) for data identifying the selected logical channel type associated with the transport channel data where a bit size of the TCTF field is selected to determine the modulo N bit size M of the MAC header. The modulo N bit size M of the MAC header is preferably 3 modulo 8 for FACH and 2 modulo 8 for RACH. 
     The TCTF data field bit size is preferably 3 with respect to FACH MAC headers associated with the CCCH, CTCH, SHCCH and BCCH logical channels. The TCTF data field bit size is preferably 5 with respect to the FACH MAC headers associated with the DCCH and DTCH logical channels. The TCTF data field bit size is preferably 2 with respect to RACH MAC headers associated with the CCCH and SHCCH logical channels. The TCTF data field bit size is preferably 4 with respect to the RACH MAC headers associated with the DCCH and DTCH logical channels. 
     Other objects and advantages will be apparent to one of ordinary skill in the art from the following detailed description of a presently preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified illustration of a wireless spread spectrum communication system. 
     FIG. 2 is an illustration of data flowing into a common or shared channel. 
     FIG. 3 is an illustration of data flowing into a FACH channel within a RNC. 
     FIG. 4 is a schematic diagram illustrating a channel mapping with respect to a MAC layer and a physical layer in a communication system according to the teaching of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a simplified wireless spread spectrum code division multiple access (CDMA) communication system  18 . A node b  26  within the system  18  communicates with associated user equipment (UE)  20 - 24  such as a mobile terminal (MT). The node b  26  has a single site controller (SC)  30  associated with either a single base station (BS)  28  (shown in FIG. 1) or multiple base stations. A Group of node bs  26 ,  32 ,  34  is connected to a radio network controller (RNC)  36 . To transfer communications between RNCs  36 - 40 , an interface (IUR)  42  between the RNCs is utilized. Each RNC  36 - 40  is connected to a mobile switching center (MSC)  44  which in turn is connected to the Core Network (CN)  46 . 
     To communicate within the system  18 , many types of communication channels are used, such as dedicated, shared and common. Dedicated physical channels transfer data between a node b  26  and a particular UE  20 - 24 . Common and shared channels are used by multiple UEs  20 - 24  or users. All of these channels carry a variety of data including traffic, control and signaling data. 
     Since shared and common channels carry data for different users, data is sent using protocol data units (PDUs) or packets. As shown in FIG. 2, to regulate the flow of data from differing sources  48 ,  50 ,  52  into a channel  56 , a controller  54  is used. 
     One common channel used for transmitting data to the UEs  20 - 24  is a forward access channel (FACH)  58 . As shown in FIG. 3, the FACH  58  originates in a RNC  36  and is sent to a node b  28 - 34  for wireless transmission as a spread spectrum signal to the UEs  20 - 24 . The FACH  58  carries several data types from various sources, such as a common control channel (CCCH), dedicated control and traffic channel (DCCH and DTCH), and a downlink and uplink shared channel (DSCH and USCH) control signaling via a shared control logical channel (SHCCH). The FACH  58  also carries control signaling out of band and similar data transmitted via the IUR  42  from other RNCs  38 - 40 , such as CCCH, DCCH and DTCH control data. 
     Various controllers are used by the RNC  36  to control the flow of data. A radio link controller (RLC)  64  handles the CCCH. A dedicated medium access controller (MAC-d)  66  handles the DCCH, and the DTCH. A shared medium access controller (MAC-sh)  68  handles the DSCH, USCH control signaling. Controlling the FACH  58  is a common medium access controller (MAC-c)  60 . 
     With reference to FIG. 4, there is illustrated a preferred channel mapping with respect to the MAC layer  70  and the physical layer  72 . The transport channels (TrCHs)  74  transport data over the physical layer  72  to associated physical channels  76 . Each of the TrCHs  74  is associated with one or more logical channels  78 . The TrCHs communicate by using transport blocks (TB) which are comprised of a MAC header and associated logical channel data in a RLC PDU. The MAC header has logical channel identification information. Preferably, the RLC PDU is defined by data octets, so that the RLC PDU bit size equals 0 modulo  8 . 
     Preferably, the TrCHs  74  include a dedicated channel (DCH), a downlink shared channel (DSCH), a common packet channel (CPCH), a random access channel (RACH), a forward access channel (FACH), a paging channel (PCH) and a broadcast channel (BCH). The associated physical channels include a dedicated physical channel (DPDCH), a physical downlink shared channel (PDSCH), a physical common packet channel (PCPCH), a physical random access channel (PRACH), a secondary common control physical channel (SCCPCH) and a primary common control physical channel (PCCPCH). Other transport and physical channels may be supported, such as an uplink shared channel (USCH) with an associated physical uplink shared channel (PUSCH). 
     The logical channels preferably include a dedicated traffic channel (DTCH), a dedicated control channel (DCCH), a shared control channel (SHCCH), a common control channel (CCCH), a common traffic channel (CTCH), a paging control channel (PCCH) and a broadcast control channel (BCCH). 
     The preferred association of transport channels with physical and logical channels is illustrated in FIG.  4 . For example, the FACH may transport data to the SCCPCH from any one of the set of logical channels including the DTCH, the DCCH, the SHCCH, the CCCH, or the CTCH. Similarly, the RACH transports data to the PRACH from any one of the set of logical channels including the DTCH, the DCCH, the SHCCH, or the CCCH. 
     In order to make efficient use of TBS size definitions, it is desirable to be able to use all specified TB sizes for all Logical Channel types supported by a respective TrCH. This allows the number of specified TFs for a TFS to be minimized thereby reducing signaling overhead, while maximizing the number of RLC PDU size options reducing the overhead associated with RLC segmentation and padding. TB and TBS assignment is accomplished without increasing MAC header sizes for TrCH logical channel combinations that support limited TB data payloads, i.e. the amount of data processed as a single unit from higher layers within MAC and RLC. 
     A bit aligned MAC header resolves both the radio resource efficiency issues associated with TB size signaling and RLC segmentation and padding overhead. The alignment is performed by maintaining the minimum size MAC headers for the Logical Channel and TrCH combinations that support limited TB data payload sizes, and increasing MAC headers for non- data payload size sensitive combinations to the same bit offset. 
     For example, if the data payload size limited combinations have MAC headers of X octets (total octets)+Y bit (extra bit offset, less than 8) sizes, and non-limited combination have headers of A octets+C bits and B octets+D bits. Then the C and D bits are adjusted to match Y bits. In some cases this means A and/or B octets must be incremented by one octet. It is not necessary for A and B octet sizes to match the X octet size since TB size=MAC header+RLC PDU and the octet aligned RLC PDU will conform to the available octet size. MAC headers less than an octet in length are permitted, and in fact desirable, in such cases X, A or B may be 0. 
     All TB sizes specified by RRC signaling for a specific TrCH channel will have a Y bit offset. That Y bit offset being applicable to the MAC headers for all Logical Channels supported by the specific TrCH. Since the MAC header octet sizes do not necessarily match between different Logical Channel types, RLC entities will correspondingly generate appropriate RLC PDU sizes to conform to the allowed TB sizes. This does not necessarily mean RLC PDU&#39;s have to be resized when switching between TrCH types, since it is always possible to adjust the difference in MAC header size between the new and old TrCH&#39;s in the allowed TB sizes. 
     With bit aligned MAC headers, each TrCH type may have a different bit aligned TB size offset. The offset is preferably defined by the most limited Logical Channel and TrCH combination block size, which is specific to the TrCH type. Therefore, each TrCH type has an independent optimized MAC header bit offset. 
     The invention has the additional benefit of removing processor intensive layer  2  bit shifting requirements in the UE and BS equipment. With a common TB size bit offset for all Logical Channels types supported by a specific TrCH, it is possible for received radio transmissions to be bit shifted by the physical layer according to higher layer requirements. It is advantageous to provide bit shifting at the physical layer which is already involved in bit manipulations without adding additional overhead, as opposed to adding this requirement to the higher layer processing requirements. 
     In 3G system design, RLC and Radio Resource Control (RRC) entities generate and expect to receive data blocks which start on octet boundaries. If MAC headers for specific TrCH&#39;s have variable bit offsets it is only possible to avoid bit shifting in BS down-link and MT up-link transmissions. In the MT down-link and BS up-link cases it is not possible for the physical layer to be aware of the higher layer logical channel type that defines the bit offset. Only if the bit offset is common for all transmissions across the specific transport channel can bit processing be avoided in communication layers  2  and  3 . 
     RRC Transport Format Set (TFS) signaling is used to defined Transport Block (TB) sizes for each define Transport Format (TF) allowed on a specific TrCH. The number of possible TB sizes should be minimized to reduce the signaling load. It is also necessary to choose TB sizes wisely since RLC PDU padding can dramatically increase transmission overhead. 
     Preferably, there is a maximum of 32 possible TB sizes in each TrCH&#39;s TFS. Specifying all 32 results in a significant signalling load that should be avoided. Although it is also important to have as many choices as possible on transport channels which have variable transmissions since RLC Acknowledged Mode (AM) and Unacknowledged Mode (UM) PDU&#39;s will be padded to match the next larger TB size when the previous lower size is exceeded. 
     The relation between RLC PDU and TB sizes is as follows: TB Size=MAC Header Size+RLC PDU Size. 
     In the preferred RLC AM and UM, the PDU size is always octet aligned and in Time Division Duplex (TDD) a variable non-octet aligned MAC header exists. Therefore, MAC individual bit offsets must be taken into account when specifying the allowed TB sizes. 
     In TDD, with the exception of DTCH/DCCH all logical channel combinations on the FACH and separately on the RACH are modified from the prior art to have the same bit offset (+2 bits for RACH and +3 bits for FACH when multiple logical channels are allowed). Table 1 reflects a preferred prior art MAC header size specification. 
     
       
         
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 TDD RACH/FACH MAC Header Sizes by Logical Channel Type 
               
             
          
           
               
                 Prior Art 
                   
                   
                   
                   
                   
                   
               
               
                 Logical 
                   
                 TCTF 
                 UE-id 
                 UE- 
                   
                 Header 
               
               
                 CH 
                 TrCH 
                 Field 
                 Type 
                 id 
                 C/T Field 
                 Size 
               
               
                   
               
               
                 DCCH/DT 
                 FACH 
                 3 
                 2 
                 16/32 
                 4 
                 25/41 
               
               
                 CH 
               
               
                 CCCH 
                 FACH 
                 3 
                 N/A 
                 N/A 
                 N/A 
                 3 
               
               
                 CTCH 
                 FACH 
                 3 
                 N/A 
                 N/A 
                 N/A 
                 3 
               
               
                 SHCCH 
                 FACH 
                 0/3 (Note 1) 
                 N/A 
                 N/A 
                 N/A 
                 0/3 
               
               
                 BCCH 
                 FACH 
                 3 
                 N/A 
                 N/A 
                 N/A 
                 3 
               
               
                 DCCH/DT 
                 RACH 
                 2 
                 2 
                 16 
                 4 
                 24 
               
               
                 CH 
               
               
                 CCCH 
                 RACH 
                 2 
                 N/A 
                 N/A 
                 N/A 
                 2 
               
               
                 SHCCH 
                 RACH 
                 0/2 (Note 1) 
                 N/A 
                 N/A 
                 N/A 
                 0/2 
               
               
                   
               
               
                 Note 1: SHCCH does not require TCTF when SHCCH is the only channel assigned to RACH or FACH.  
               
             
          
         
       
     
     With the prior art MAC header definitions, octet aligned AM and UM RLC payloads will result in two possible TB size bit offsets on RACH and FACH when multiple logical channel types are applied. Octet+1 or 3 bits for FACH and octet+0 or 2 bits for RACH. This potentially doubles the number of Transport Formats that need to be specified on RACH and FACH. 
     To increase the efficiency of TFS signaling and allow for more RLC PDU size choices, it is necessary to have a common TB size bit offset. Increasing MAC header sizes for CCCH, SHCCH, CTCH and BCCH, should be avoided since these channels operate in RLC TM where RLC segmentation across multiple radio frame TTIs is not possible. Therefore, the preferred solution is to increase the DCCH/DTCH TCTF by 2 bits on RACH and FACH. A preferred coding is reflected in Tables 2 and 3 below, respectively for FACH and RACH. This results in common RACH TB sizes of octet+2, i.e. 2 modulo 8, and FACH TB sizes of octet+3, i.e. 3 modulo 8. 
     Another benefit of MAC header bit alignment is the ability to remove the UE and RNC layer  2  bit shifting requirement. The RLC generates and expects to receive octet aligned PDU&#39;s. With variable bit shifted MAC headers only the UTRAN Down Link (DL) and UE Up Link (UL) MAC PDU&#39;s could avoid layer  2  bit shifting by padding the MAC header and providing a padding indicator to the physical layer. This is not possible for the UE DL and UTRAN UL transmissions since physical layer is unaware of the logical channel type on RACH and FACH. 
     If the TrCH bit offset is constant for all logical channel types supported for a given TrCH, the physical layer can pad the MAC header to octet align the UE DL and UTRAN UL. No padding indicator is needed in UL or DL since the padding is constant for the TrCH. 
     The number of TFs specifying TB sizes allowed in each TFS on a specific TrCH should be minimized to reduce the layer  3  signaling load. It is also necessary to allow a maximum number of octet aligned RLC PDU sizes in AM and UM for efficient transfer of DCCH/DTCH data. In TDD mode bit shifted MAC headers potentially doubles the number of TFs that need to be defined on RACH and FACH TrCHs. Additionally, variable bit shifted MAC headers result in requiring layer  2  bit shifting for all UE DL and UTRAN UL transmissions on RACH and FACH. MAC header bit alignment is defined to avoid duplication of TB size definitions for octet aligned RLC PDUs and layer  2  bit shifting. 
     As in the prior art, the MAC header preferably includes a Target Channel Type Field (TCTF). The TCTF field is a flag that provides identification of the logical channel type on FACH and RACH transport channels, i.e. whether it carries BCCH, CCCH, CTCH, SHCCH or dedicated logical channel information. Unlike the prior art, the preferred size and coding of TCTF for TDD are shown in Tables 2 and 3. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Coding of the Target Channel Type Field on FACH for TDD 
               
             
          
           
               
                 TCTF 
                 Designation 
               
               
                   
               
               
                 000 
                 BCCH 
               
               
                 001 
                 CCCH 
               
               
                 010 
                 CTCH 
               
               
                 01100 
                 DCCH or DTCH 
               
               
                   
                 Over FACH 
               
               
                 01101- 
                 Reserved 
               
               
                 01111 
                 (PDUs with this coding will be discarded by this version of the 
               
               
                   
                 protocol) 
               
               
                 100 
                 SHCCH 
               
               
                 101- 
                 Reserved 
               
               
                 111 
                 (PDUs with this coding will be discarded by this version of the 
               
               
                   
                 protocol) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Coding of the Target Channel Type Field on RACH for TDD 
               
             
          
           
               
                 TCTF 
                 Designation 
               
               
                   
               
               
                 00 
                 CCCH 
               
               
                 0100 
                 DCCH or DTCH 
               
               
                   
                 Over RACH 
               
               
                 0101- 
                 Reserved 
               
               
                 0111 
                 (PDUs with this coding will be discarded by this version of the 
               
               
                   
                 protocol) 
               
               
                 10 
                 SHCCH 
               
               
                 11 
                 Reserved 
               
               
                   
                 (PDUs with this coding will be discarded by this version of the 
               
               
                   
                 protocol) 
               
               
                   
               
               
                 Note that the preferred size of the TCTF field of FACH for TDD is either 3 or 5 bits depending on the value of the 3 most significant bits. The preferred TCTF of the RACH for TDD is either 2 or 4 bits depending on the value of the 2 most significant bits.  
               
             
          
         
       
     
     Bit aligned MAC headers allow common TB sizes to be defined for different logical channels on the same TrCH. Common TB sizes reduce signalling overhead and potentially increase the options for RLC PDU sizes, which increases system efficiency by reducing the need for padding in AM and UM. 
     This is especially important for RACH and FACH channels where a common TrCH supports many different traffic types. Optimally for RACH and FACH, each TB size specified can apply to DCCH, CCCH, CTCH, SHCCH and DTCH. To allow this capability in octet mode it is preferred to specify the total number of octets not just the number of RLC PDU octets. 
     By specifying the total number of octets, it is not necessary to indicate the TDD MAC header type on common channels since the header offset is the same for all logical channel types. It is also possible to avoid RLC PDU resizing transport channel switching by taking into account the change in MAC header octet offset. 
     Table 4 is a preferred specification for a Transport Format Set (TFS) in a 3G system. 
     
       
         
               
             
               
               
               
               
               
             
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Transport Format Set (TFS) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Information 
                   
                   
                 Type and 
                 Semantics 
               
               
                 Element/Group name 
                 Need 
                 Multi 
                 reference 
                 description 
               
               
                   
               
               
                 CHOICE Transport 
                 MP 
               
               
                 channel type 
               
               
                 &gt;Dedicated transport 
                   
                   
                   
                 The transport 
               
               
                 channels 
                   
                   
                   
                 channel that is 
               
               
                   
                   
                   
                   
                 configured with 
               
               
                   
                   
                   
                   
                 this TFS is 
               
               
                   
                   
                   
                   
                 of type DCH 
               
               
                 &gt;&gt;Dynamic Transport 
                 MP 
                 1 to 
                   
                 Note 1 
               
               
                 Format Information 
                   
                 &lt;max TF&gt; 
               
               
                 &gt;&gt;&gt;RLC Size 
                 MP 
                   
                 Integer 
                 Unit is bits 
               
               
                   
                   
                   
                 (0 . . . 4992) 
                 Note 2 
               
               
                 &gt;&gt;&gt;Number of TBs 
                 MP 
                 1 to 
                   
                 Present for 
               
               
                 and TTI List 
                   
                 &lt;maxTF&gt; 
                   
                 every valid 
               
               
                   
                   
                   
                   
                 number of 
               
               
                   
                   
                   
                   
                 TB&#39;s (and 
               
               
                   
                   
                   
                   
                 TTI) for this 
               
               
                   
                   
                   
                   
                 RLC Size. 
               
               
                 &gt;&gt;&gt;&gt;Transmission 
                 CV- 
                   
                 Integer 
                 Unit is ms. 
               
               
                 Time Interval 
                 dyna- 
                   
                 (10, 20, 
               
               
                   
                 mic 
                   
                 40, 80) 
               
               
                   
                 TTI 
               
               
                 &gt;&gt;&gt;&gt;Number of 
                 MP 
                   
                 Integer 
                 Note 3 
               
               
                 Transport blocks 
                   
                   
                 (0 . . . 512) 
               
               
                 &gt;Common transport 
                   
                   
                   
                 The transport 
               
               
                 channels 
                   
                   
                   
                 channel that is 
               
               
                   
                   
                   
                   
                 configured with 
               
               
                   
                   
                   
                   
                 this TFS is of 
               
               
                   
                   
                   
                   
                 a type not 
               
               
                   
                   
                   
                   
                 equal to DCH 
               
               
                 &gt;&gt;Dynamic Transport 
                 MP 
                 1 to 
                   
                 Note 
               
               
                 Format Information 
                   
                 &lt;maxTF&gt; 
               
               
                 &gt;&gt;&gt;RLC Size 
                 MP 
                   
                 Integer 
                 Unit is bits 
               
               
                   
                   
                   
                 (0 . . . 4992) 
                 Note 2 
               
               
                 &gt;&gt;&gt;Number of TBs 
                 MP 
                 1 to 
                   
                 Present for 
               
               
                 and TTI List 
                   
                 &lt;maxTF&gt; 
                   
                 every valid 
               
               
                   
                   
                   
                   
                 number of 
               
               
                   
                   
                   
                   
                 TB&#39;s (and 
               
               
                   
                   
                   
                   
                 TTI) for 
               
               
                   
                   
                   
                   
                 this RLC Size. 
               
               
                 &gt;&gt;&gt;&gt;Number of 
                 MP 
                   
                 Integer 
                 Note 3 
               
               
                 Transport blocks 
                   
                   
                 0 . . . 512) 
               
               
                 &gt;&gt;&gt;&gt;CHOICE mode 
                 MP 
               
               
                 &gt;&gt;&gt;&gt;&gt;FDD 
                   
                   
                   
                 (no data) 
               
               
                 &gt;&gt;&gt;&gt;&gt;TDD 
               
               
                 &gt;&gt;&gt;&gt;&gt;&gt;Transmission 
                 CV- 
                   
                 Integer 
                 Unit is ms. 
               
               
                 Time Interval 
                 dyna- 
                   
                 (10, 20, 
               
               
                   
                 mic 
                   
                 40, 80) 
               
               
                   
                 TTI 
               
               
                 &gt;&gt;&gt;CHOICE Logical 
                 MP 
                   
                   
                 The logical 
               
               
                 Channel List 
                   
                   
                   
                 channels that 
               
               
                   
                   
                   
                   
                 are allowed 
               
               
                   
                   
                   
                   
                 to use this 
               
               
                   
                   
                   
                   
                 RLC Size 
               
               
                 &gt;&gt;&gt;&gt;ALL 
                   
                   
                 Null 
                 All logical 
               
               
                   
                   
                   
                   
                 channels 
               
               
                   
                   
                   
                   
                 mapped to this 
               
               
                   
                   
                   
                   
                 transport 
               
               
                   
                   
                   
                   
                 channel. 
               
               
                 &gt;&gt;&gt;&gt;Configured 
                   
                   
                 Null 
                 The logical 
               
               
                   
                   
                   
                   
                 channels confi- 
               
               
                   
                   
                   
                   
                 gured to use 
               
               
                   
                   
                   
                   
                 this RLC size 
               
               
                   
                   
                   
                   
                 in the RB map- 
               
               
                   
                   
                   
                   
                 ping info. 
               
               
                   
                   
                   
                   
                 10.3.4.21 if 
               
               
                   
                   
                   
                   
                 present in this 
               
               
                   
                   
                   
                   
                 message or in 
               
               
                   
                   
                   
                   
                 the previously 
               
               
                   
                   
                   
                   
                 stored con- 
               
               
                   
                   
                   
                   
                 figuration 
               
               
                   
                   
                   
                   
                 otherwise 
               
               
                 &gt;&gt;&gt;&gt;Explicit List 
                   
                 1 to 15 
                   
                 Lists the logi- 
               
               
                   
                   
                   
                   
                 cal channels 
               
               
                   
                   
                   
                   
                 that are allow- 
               
               
                   
                   
                   
                   
                 ed to use this 
               
               
                   
                   
                   
                   
                 RLC size. 
               
               
                 &gt;&gt;&gt;&gt;&gt;RB Identity 
                 MP 
                   
                 RB 
               
               
                   
                   
                   
                 identity 
               
               
                   
                   
                   
                 10.3.4.16 
               
               
                 &gt;&gt;&gt;&gt;&gt;Logical 
                 CV- 
                   
                 Integer 
                 Indicates the 
               
               
                 Channel 
                 UL- 
                   
                 (0 . . . 1) 
                 relevant UL 
               
               
                   
                 RLC 
                   
                   
                 logical channel 
               
               
                   
                 Logi- 
                   
                   
                 for this RB. 
               
               
                   
                 cal 
                   
                   
                 “0” corres- 
               
               
                   
                 Chan- 
                   
                   
                 ponds to the 
               
               
                   
                 nels 
                   
                   
                 first, “1” 
               
               
                   
                   
                   
                   
                 corresponds to 
               
               
                   
                   
                   
                   
                 the second UL 
               
               
                   
                   
                   
                   
                 logical channel 
               
               
                   
                   
                   
                   
                 configured for 
               
               
                   
                   
                   
                   
                 this RB in the 
               
               
                   
                   
                   
                   
                 IE “RB map- 
               
               
                   
                   
                   
                   
                 ping info”. 
               
               
                 &gt;&gt;Semi-static 
                 MP 
                   
                 Semi-static 
               
               
                 Transport 
                   
                   
                 Transport 
               
               
                 Format Information 
                   
                   
                 Format 
               
               
                   
                   
                   
                 Information 
               
               
                   
                   
                   
                 10.3.5.11 
               
               
                   
               
             
          
           
               
                 Condition 
                 Explanation 
               
               
                   
               
               
                 DynamicTTI 
                 This IE is included if dynamic TTI usage 
               
               
                   
                 is indicated in IE Transmission Time 
               
               
                   
                 Interval in Semi-static Transport Format 
               
               
                   
                 Information. Otherwise it is not needed. 
               
               
                 UL-RLCLogicalChannels 
                 If “Number of uplink RLC logical 
               
               
                   
                 channels” in IE “RB mapping info” in 
               
               
                   
                 this message is 2 or the IE “RB mapping 
               
               
                   
                 info” is not present in this message and 2 
               
               
                   
                 UL logical channels are configured for 
               
               
                   
                 this RB, then this IE is present. 
               
               
                   
                 Otherwise this IE is not needed. 
               
               
                   
               
               
                 NOTE: The parameter “rate matching attribute” is in line with the RAN WG1 specifications. However, it is not currently in line with the description in 25.302.  
               
               
                 NOTE 1: The first instance of the parameter Number of TBs and TTI List within the Dynamic transport format information correspond to transport format 0 for this transport channel, the second to transport format 1 and so on. The total number of configured transport formats for each transport channel does not exceed &lt;maxTF&gt;.  
               
               
                 NOTE 2: For dedicated channels, ‘RLC size’ reflects RLC PDU size. In FDD for common channels ‘RLC size’ reflects actual TB size. In TDD for common channels since MAC headers are not octet aligned, to calculate TB size the MAC header bit offset is added to the specified size (similar to the dedicated case). Therefore for TDD DCH TrCHs the 4 bit C/T is added if MAC multiplexing is applied, for FACH the 3 bit TCTF offset is added and for RACH the 2 bit TCTF offset is added.  
               
               
                 NOTE 3: If the number of transport blocks &lt;&gt; 0, and Optional IE “CHOICE RLC mode” or “CHOICE Transport block size is absent, it implies that no RLC PDU data exists but only parity bits exist. If the number of transport blocks = 0, it implies that neither RLC PDU data nor parity bits exist. In order to ensure the possibility of CRC based Blind Transport Format Detection, UTRAN should configure a transport format with number of transport block  
               
               
                 #&lt;&gt; 0, with a zero-size transport block.  
               
             
          
         
       
     
     References 
     1. 3GPP TSG-RAN Working Group 2 Meeting #10, Tdoc R2-00-057 
     2. 3GPP TSG-RAN Working Group 2 Meeting #10, Tdoc R2-00-060 
     The following is a listing of acronyms and their meanings as used herein: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 AM 
                 Acknowledged Mode 
               
               
                   
                 BCCH 
                 Broadcast Control Channel 
               
               
                   
                 BCH 
                 Broadcast Channel 
               
               
                   
                 BS 
                 Base Station 
               
               
                   
                 CCCH 
                 Common Control Channel 
               
               
                   
                 CDMA 
                 Code Division Multiple Access 
               
               
                   
                 CN 
                 Core Network 
               
               
                   
                 CPCH 
                 Common Packet Channel 
               
               
                   
                 CTCH 
                 Common Traffic Channel 
               
               
                   
                 DCCH 
                 Dedicated Control Channel 
               
               
                   
                 DCH 
                 Dedicated Channel 
               
               
                   
                 DL 
                 Down Link 
               
               
                   
                 DPDCH 
                 Dedicated Physical Channel 
               
               
                   
                 DPSCH 
                 Physical Downlink Shared 
               
               
                   
                   
                 Channel 
               
               
                   
                 DSCH 
                 Downlink Shared Channel 
               
               
                   
                 DTCH 
                 Dedicated Traffic Channel 
               
               
                   
                 FACH 
                 Forward Acess Channel 
               
               
                   
                 MAC 
                 Medium Access Control 
               
               
                   
                 MAC-c 
                 Common Medium Access Control 
               
               
                   
                 MAC-d 
                 Dedicated Medium Access 
               
               
                   
                   
                 Control 
               
               
                   
                 MAC-sh 
                 Shared Medium Access Control 
               
               
                   
                 MSC 
                 Mobile Switching Center 
               
               
                   
                 MT 
                 Mobile Terminal 
               
               
                   
                 NRT 
                 Non-Real Time 
               
               
                   
                 PCCPCH 
                 Primary Common Control 
               
               
                   
                   
                 Physical Channel 
               
               
                   
                 PCH 
                 Paging Channel 
               
               
                   
                 PCPCH 
                 Physical Common Packet Channel 
               
               
                   
                 PDU 
                 Protocol Data Units 
               
               
                   
                 PRACH 
                 Physical Random Access Channel 
               
               
                   
                 PUSCH 
                 Physical Uplink Shared Channel 
               
               
                   
                 RACH 
                 Random Access Channel 
               
               
                   
                 RAN 
                 Radio Access Network 
               
               
                   
                 RLC 
                 Radio Link Control 
               
               
                   
                 RNC 
                 Radio Network Controller 
               
               
                   
                 RRC 
                 Radio Resource Control 
               
               
                   
                 SC 
                 Site Controller 
               
               
                   
                 SCCPCH 
                 Secondary Common Control 
               
               
                   
                   
                 Physical Channel 
               
               
                   
                 SHCCH 
                 Shared Channel Control Channel 
               
               
                   
                 TB 
                 Transport Block 
               
               
                   
                 TCTF 
                 Target Channel Type Field 
               
               
                   
                 TDD 
                 Time Division Duplex 
               
               
                   
                 TF 
                 Transport Format 
               
               
                   
                 TFS 
                 Transport Format Set 
               
               
                   
                 TrCH 
                 Transport Channel 
               
               
                   
                 UE 
                 User Equipment 
               
               
                   
                 UL 
                 Up Link 
               
               
                   
                 UM 
                 Unacknowledged Mode 
               
               
                   
                 USCH 
                 Uplink Shared Channel