3G/UMTS-TDSCDMA

Midamble/Channelization Code

Midamble is a reference signal located in the middle of a slot which is designed to help decoding slot's user data. (For the details of slot structure, refer to the slot structure section in Frame Structure page)

Midamble and possible channelization code for a slot closely related and the midamble configuration and channelization code used for a slot is specified in RRC Connection Setup or Radio Bearer Setup message as shown below.

            | +-dl-InformationPerRL-List ::= SEQUENCE OF SIZE(1..maxRL[8]) [1] OPTIONAL:Exist

            |   +-DL-InformationPerRL-r4 ::= SEQUENCE [100]

            |     +-modeSpecificInfo ::= CHOICE [tdd]

            |     +-dl-DPCH-InfoPerRL ::= CHOICE [tdd] OPTIONAL:Exist

            |     | +-tdd ::= SEQUENCE [10]

            |     |   +-dl-CCTrChListToEstablish ::= SEQUENCE OF SIZE(1..maxCCTrCH[8]) [1] OPTIONAL:Exist

            |     |   | +-DL-CCTrCh-r4 ::= SEQUENCE [110]

            |     |   |   +-tddOption ::= CHOICE [tdd128]

            |     |   |   | +-tdd128 ::= SEQUENCE [1]

            |     |   |   |   +-dl-CCTrCH-TimeslotsCodes ::= SEQUENCE OPTIONAL:Exist

            |     |   |   |     +-firstIndividualTimeslotInfo ::= SEQUENCE [0]

            |     |   |   |     | +-timeslotNumber ::= INTEGER (0..6) [6]

            |     |   |   |     | +-tfci-Existence ::= BOOLEAN [TRUE]

            |     |   |   |     | +-midambleShiftAndBurstType ::= SEQUENCE

            |     |   |   |     | | +-midambleAllocationMode ::= CHOICE [defaultMidamble]

            |     |   |   |     | | | +-defaultMidamble ::= NULL

            |     |   |   |     | | +-midambleConfiguration ::= INTEGER (1..8) [4]

            |     |   |   |     | +-modulation ::= ENUMERATED [mod-QPSK]

            |     |   |   |     | +-ss-TPC-Symbols ::= ENUMERATED [one]

            |     |   |   |     | +-additionalSS-TPC-Symbols ::= INTEGER OPTIONAL:Omit

            |     |   |   |     +-dl-TS-ChannelisationCodesShort ::= SEQUENCE

            |     |   |   |     | +-codesRepresentation ::= CHOICE [bitmap]

            |     |   |   |     |   +-bitmap ::= BIT STRING  [0000000011111111]

            |     |   |   |     +-moreTimeslots ::= CHOICE [noMore]

            |     |   |   |       +-noMore ::= NULL

The Association between Midambles and Channelisation Codes for default midamble allocation is specifed in 25.221 AA.2 and AA.3.

For example, AA.2 defines Association between Midambles and Channelisation Codes for default midamble allocation which specifies the following cases.

Most commonly used case is K=8. The K value is specified by '2 x midambleConfiguration in RRC message'. For example, if midambleConfiguration in Radio Bearer Setup message is 4, the K value becomes 8. So if the midambleAllocationMode is 'DefaultMidamble', midambleConfiguration is 4, we have to apply the association tree of AA.2.5 Association for K=8 Midambles

• AA.2.1 Association for K=16 Midambles
• AA.2.2 Association for K=14 Midambles
• AA.2.3 Association for K=12 Midambles
• AA.2.4 Association for K=10 Midambles
• AA.2.5 Association for K=8 Midambles
• AA.2.6 Association for K=6 Midambles
• AA.2.7 Association for K=4 Midambles
• AA.2.8 Association for K=2 Midambles

Now let's look into howto interpret the association tree with an example. First, you need to understand the meaning of the symbol in the mapping tree. The symbol is represented in the following format.

Following is the association tree for AA.2.5 Association for K=8 Midambles. With the symbol interpretation shown above, I think you can make sense out of the tree.