W-CDMA - Terms

RB - Radio Bearer

The service provided by the Layer 2 for the transfer of user data between UE (User Equipment) and UTRAN (UMTS Terrestrial Radio Access Network). Also in page 28, 25.321: “Dynamic radio bearer control is performed by RRC, based on the traffic volume measurements reported by MAC.” Each User Entity may have several RBs. The maximum number of RBs for each User Entity supported at current release is:
1. Maximum=5: e.g. 1 signalling channel + 3 voice channels + 1 data channel;
2. Maximum=32: for all other configurations

RAB - Radio Access Bearer

Term used in UMTS to identify the service the AS (Access Stratum) provides to the NAS (Non Access Stratum) for transfer of user data between the UE (User Equipment) and the CN (Core Network).

CPCH - Common Packet Channel
This is a contention based UMTS channel used for transmission of bursty data traffic. This channel only exists in FDD (Frequency Division Duplex) mode and only in the uplink direction. The common packet channel is shared by the UE (User Equipment) in a cell and therefore, it is a common resource. The CPCH employs fast power control.

TFI - Transport Format Indicator
The Transport Format Indicator indicates the local UMTS air interface transport format to be used for the transmission time interval.

TFCI - Transport Format Combination Indicator
This is a representation of the current TFC (Transport Format Combination) being used. The TFCI is transferred across the air interface and allows the receiving layers to identify the current valid Transport Format Combination and hence, how to decode, de-multiplex and deliver the received data on the appropriate Transport Channels.

TCTF - Target Channel Type Field
The UMTS air interface uses the Target Channel Type Field to provide identification of the logical channel class on the FACH (Forward Access Channel) and RACH (Random Access Channel) transport channels. TCTF indicates if BCCH (Broadcast Control Channel), CCCH (Common Control Channel), CTCH (Common Traffic Channel), SHCCH (Shared Channel Control Channel) or dedicated logical channel information is being transported.

TB - Transport Block
In UMTS a TB (Transport Block) is defined as the data accepted by the physical layer to be jointly encoded. The transmission block timing is then tied exactly to this Layer 1 frame timing, e.g. every transmission block is generated precisely every 10ms, or a multiple of 10ms. Also in page 23, 25.321:”The Transport Blocks, shall be transmitted in the order as delivered from RLC. When multiplexing of RLC PDUs from different logical channels is performed on MAC, the order of all Transport Blocks originating from the same logical channel shall be the same as the order of the sequence delivered from RLC. The order of the different logical channels in a TBS is set by the MAC protocol.”

TBS - Transport Block Set
The Transport Block is defined as a set of Transport Blocks, which are exchanged between MAC and L1 at the same time instance using the same transport channel. A high rate transport channel carries more information and therefore potentially carries more transport blocks. Also in page 23, 25.321:”In the uplink, all MAC PDUs delivered to the physical layer within one TTI are defined as TBS. It consists of one or several TBs, each containing one MAC PDU.”

Transport Block Size

The Transport Block Size is the defined number of bits in a Transport Block. The Transport Block Size is always fixed within a given Transport Block Set. That is all Transport Blocks within a Transport Block Set are equally sized.

Transport Block Set Size
The Transport Block Set Size is defined as the number of bits in a Transport Block Set.

TTI - Transmission Time Interval
This is defined as the inter-arrival time of TBS (Transport Block Set), and is equal to the periodicity at which a Transport Block Set is transferred by the physical layer on the radio interface. It is always a multiple of the minimum interleaving period (e.g. 10ms, the length of one RF (Radio Frame)). The MAC (Medium Access Control) delivers one Transport Block Set to the physical layer every TTI.

Transport Bearer:
Service provided by the transport layer and used by frame protocol for the delivery of FP PDU

Transport Format
Transport Format is defined as a combination of attributes which include: error protection, timing, interleaving, bit rate and mapping onto physical channels.

TFS - Transport Format Set
The Transport Format Set is the set of different Transport Formats associated to a Transport Channel.

TFCS - Transport Format Combination Set
The Transport Format Combination Set is defined as a set of Transport Format Combinations on a Coded Composite Transport Channel.

CCTrCH (Coded Composite Transport Channel)
A data stream resulting from encoding and multiplexing of one or several transport channels.

TFC - Transport Format Combination
The physical layer multiplexes one or several Transport Channels onto a Coded Composite Transport Channel (CCTrCH). These Transport Channels each have defined transport formats (maybe from a Transport Format Set) which are applicable. However, at a given point of time, not all combinations of transport channels and their associated formats are permitted, hence a subset is defined. The Transport Format Combination is one of the subset, which identifies the transport channels with their chosen format that will make up the Coded Composite Transport Channel.

CFN (Connection Frame Number)
CFN counter. CFN is the frame counter used for the L2/transport channel synchronisation between UE and UTRAN. A CFN value is associated to each TBS and it is passed together the MAC-L1 SAP. CFN provides a common frame reference (at L2) to be used e.g. for synchronised transport channel reconfiguration.
The duration of the CFN cycle is longer than the maximum allowed transport delay between MAC and L1 (in UTRAN side, between SRNC and Node B, because the L1 functions that handle the transport channel synchronisation are in the Node B). Range: from 1 to 255 frames. When used for PCH the range is 0 to 4095 frames.