Transmisson Parameter Signaling (TPS) in DVB-H
1). Service discovery signaling in DVB-H
§ Service discovery signaling within DVB-H is considered to consist of two parts: transmission parameter signaling (TPS) and Program-Specific Information/ Service Information (PSI/SI).
§ TPS is carried as part of the physical layer (L1)
§ PSI/SI is carried within the data link layer (L2).
§ http://docs.google.com/View?id=ddh56dhg_1733wv4htpg
2). TPS Overview
§ Transmisson Parameter Signaling (TPS): Some additional signaling bits have been introduced to indicate whether DVB-H services are present in the multiplex, and if MPE-FEC is in use.
§ TPS (Transmission Parameter Signaling): Allows transmission of enough information about the services carried by the multiplex, thus enhancing and speeding up service discovery.
§ TPS-bit signalling provides robust multiplex level signalling capability to the DVB-T/H transmission system.
§ TPS is known to be very robust signalling channel as a TPS-lock in a demodulator can be achieved with a very low C/N-value.
§ It is also much faster to demodulate the information carried in the TPS than for example in SI or in the MPE-header.
§ Accordingly, they have been used in DVB-H to signal both the time slicing and MPE-FEC as well as the 4K mode option.
Unused combinations of the precious TPS bits have been used to signal the new DVB-H transmission parameters:
§ The 4K mode, to be used for dedicated DVB-H networks, is signalled as an additional transmission mode to the existing 2K and 8K modes.
§ The DVB-T hierarchy information is used to specify the symbol interleaver depth (i.e. native or in-depth).
§ The Cell Identifier, which is optional for traditional DVB-T services, becomes mandatory in DVB-H.
§ Please notice that in the case of SFN networks, there is only one cell identifier for the whole network.
Two formerly unused TPS bits have been allocated for DVB-H signalling:
§ A time slicing indicator to signal that at least one time-sliced DVB-H service is available in the transmission channel.
§ A MPE-FEC indicator to signal that at least one DVB-H service in the transmission channel is protected by MPE-FEC.
3). TPS signalling information and format
§ TPS consists of L1 service discovery parameters and is carried within the orthogonal frequency division multiplexing (OFDM) frames.
§ It is defined over 68 consecutive OFDM symbols per one OFDM frame.
§ One OFDM superframe is composed of four sequential OFDM frames, and one TPS bit is conveyed within each OFDM symbol.
§ TPS bits are categorized as follows: 1 initialization bit, 16 synchronization bits, 37 information bits, and 14 redundancy bits for error protection.
§ TPS is an important part of the service discovery within DVB-H.
§ The DVB-H indicator bit is used for an early elimination of signals that are not supporting DVB-H.
§ The MPE-FEC indicator bit enables the receiver to prepare different reception strategies, depending on whether the MPE-FEC is supported.
The DVB-H physical layer should include:
§ Signaling in TPS-bits (Transmisson Parameter Signaling) to enhance and speed up service discovery.
§ A cell identifier is also carried in TPS-bits to support quicker signal scan and frequency handover on mobile receivers.
| Bit number | Format (EN 300 744) | Purpose/Content |
| s0 | see clause | Initialization - is an initialization bit for the differential 2-PSK modulation. |
| s1to s16 | 0011010111101110 or 1100101000010001 | Synchronization word The first and third TPS block in each super-frame have the following synchronization word: s1 - s16 = 0011010111101110. The second and fourth TPS block have the following synchronization word: s1 - s16 = 1100101000010001. |
| s17 to s22 | see clause | Length indicator (see annex F) is used as a TPS length indicator (binary count starting from and including bit s17) to signal the number of used bits of the TPS. |
| s23, s24 | see table 10 | Frame number Four frames constitute one super-frame. The frames inside the super-frame are numbered from 1 to 4. |
| s25, s26 | see table 11 | Constellation In order to determine the modulation scheme (00=QPSK, 01=16-QAM, 10=64-QAM, 11=Reserved) |
| s27, s28, s29 | see table 12 | Hierarchy information (see annex F) specifies whether the transmission is hierarchical |
| s30, s31, s32 | see table 13 | Code rate, HP stream code rate for the HP level (r1) of the modulation |
| s33, s34, s35 | see table 13 | Code rate, LP stream code rate for the LP level (r2) |
| s36, s37 | see table 14 | Guard interval |
| s38, s39 | see table 15 | Transmission mode (see annex F) signal the transmission mode (2K mode or 8K mode). |
| s40 to s47 | see clause | Cell identifier identify the cell from which the signal comes from |
| s48 to s53 | all set to | See annex F |
| s54 to s67 | BCH code | Error protection |
DVB-H signalling: Bits s48 and s49 shall be used to indicate to the receivers the transmission of DVB-H services.
§ In case of Hierarchical transmission, the signification of bits s48 and s49 varies with the parity of the OFDM frame transmitted, as follows:
§ When received during OFDM frame number 1 and 3 of each super frame, DVB-H signalling shall be interpreted as in relation with the High Priority stream (HP)
§ When received during OFDM frame number 2 and 4 of each super frame, DVB-H signalling shall be interpreted in relation with the Low Priority stream (LP)
| s48 | s49 | DVB-H signalling |
| 0 | x | Time Slicing is not used |
| 1 | x | At least one elementary stream uses Time Slicing |
| x | 0 | MPE-FEC not used |
| x | 1 | At least one elementary stream uses MPE-FEC |
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