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Test transmitters

TV Test Transmitter R&S SFQ / R&S SFL ISDB-T – Digital terrestrial broadcasting in

The transition from analog to digital

broadcast transmission is occurring

everywhere: in broadband commu-

nication networks, satellite trans-

mission and terrestrial broad-

casting. The ISDB-T standard is

about to be launched in Japan, and

Rohde & Schwarz is involved in the development and production with its

TV Test Transmitters R&S SFQ and

R&S SFL (FIG 1).

43961

FIG 1 The two TV Test Transmitters R&S SFQ and R&S SFL-I handle the ISDB-T standard.

ISDB-T: one standard for TV, ing and data services. Thus, the Japa- sound broadcasting and data nese broadcasting standard ISDB-T (Ter- services restrial Integrated Services Digital Broad- casting) was established, in which these In the 90s the Japanese Association of services can be transmitted separately Radio Industries and Business (ARIB) in a large number of combinations [1, 2]. developed a transmission standard for Currently, comprehensive tests are digital terrestrial broadcasting. Unlike in taking place in several regions in Japan, other parts of the world, just one stan- dard was to cover TV, sound broadcast-

32 News from Rohde&Schwarz Number 177 (2003/I) confirming the system’s performance. FIG 2 Testing includes the following: ISDB-T spectrum. ◆ TV, radio data transmission and sound broadcasting ◆ Mobile multimedia services ◆ Feeding into cable networks ◆ Emergency services ◆ TV shopping, shopping information services and pay TV ◆ Single networks (SFN) in buildings, at sea and in the mountains ◆ On-demand services, etc

The system’s special strengths are SFN, the positive characteristics in mobile reception, possible narrowband recep- tion where only some of the transmit- ted data is evaluated (partial reception) as well as the hierarchical transmission for adaptation to different receive con- ditions.

The field test results will come in useful when regular ISDB-T operation is intro- duced in the three main regions of Tokyo, ISDB-T characteristics nel uses orthogonal frequency division Nagoya and Osaka between 2003 and (OFDM), which is state-of- 2005. By 2006, ISDB-T is to cover all of For both ISDB-T and the other digital the-art technology in terrestrial digital Japan so that analog TV broadcasting TV standards (e.g. DVB-T), the MPEG2 TV broadcasting. The transmission band- can be discontinued in 2010. method was chosen as the source width is 5.6 MHz, making the signal suit- coding for the digital TV signals to be able for transmission in a 6 MHz channel transmitted. The RF transmission chan- (FIG 2 and 3).

Hierarchical transmission Up to three different services with dif- ferent transmission parameters can be sent simultaneously in a transmission channel. This method is referred to as

FIG 3 Transmission parameters for ISDB-T (6 MHz channel). hierarchical transmission and gener- ally addresses various types of receiv- Mode 1 Mode 2 Mode 3 ers (FIG 4). A 6 MHz channel can thus Number of segments 13 provide different services with the same 5.575 MHz 5.573 MHz 5.572 MHz infrastructure. For example, a stationary Carrier offset 3.968 kHz 1.984 kHz 0.992 kHz TV receiver is supplied with an HDTV pro- Number of carriers 1405 2809 5617 gram while mobile TV receivers in a tour Carrier modulation QPSK, 16QAM, 64QAM, DQPSK bus receive a TV picture at reduced res- Symbols per frame 204 olution and portable receivers in mobile Symbol duration (actual) 252 µs 504 µs 1008 µs phone format get the same TV program Guard interval 1/4, 1/8, 1/16, 1/32 at a suitably reduced resolution. Auxil- IFFT length 2K 4K 8K iary information about the current pro- Inner Convolutional code (1/2, 2/3, 3/4, 5/6, 7/8) gram can be transmitted and retrieved Outer code Reed-Solomon (204,188) by the viewer, if required.

33 News from Rohde&Schwarz Number 177 (2003/I) BROADCASTING Test transmitters

Partial reception Audio /data HDTV Audio / SDTV SDTV Partial reception of the broadcasting data (mobile reception) (stationary reception) spectrum is a special case of hierarchical transmission. The OFDM spectrum con- sists of 13 segments (FIG 4). If the influ- ence range of the transmission param- eters is limited to one OFDM segment, Spectrum Spectrum this segment can be received indepen- dently of the other 12 segments. A nar- rowband receiver evaluating only this 5.6 MHz 5.6 MHz OFDM segment receives a complete signal. If suitable transmission param- eters are selected, this segment can be Broadband Narrowband designed to be particularly immune to ISDB-T receiver ISDB-T receiver interference. Thus, the available ser- vices especially address mobile and por- FIG 4 Schematic of hierarchical transmission and partial reception. table receivers, e.g. mobile phones and personal digital assistants (PDA). Appli- cation examples are the downstream for mobile or the download of , The subsequent energy dispersal The following bytewise interleaver sep- audio and software. module adds a pseudo random binary arates adjacent data by rearranging the sequence (PRBS) to the data stream to sequence. Burst-like errors often occur Channel coding ensure a sufficient number of binary in the transmission channel, always FIG 5 shows the functional design changes. interfering with subsequent data. How- of channel coding with ISDB-T. Basi- ever, the de-interleaver in the receiver cally, three identical paths (hierarchical Depending on the two transmission restores the original data sequence. coding) are provided. parameters ”modulation” and ”code During this process, burst errors are rate”, the different delays of the data sorted into single errors that can then be First, the transport stream passes streams in the three paths are caused corrected by the Reed-Solomon decoder. through the outer coder where the Reed- by bytewise interleaving in the transmit- Solomon code is applied to every trans- ter and de-interleaving in the receiver. The convolutional coder with integrated port stream packet, which enables the A delay adjustment is performed in the puncturer adds further redundancy to receiver to correct up to eight erroneous coder to minimize receiver delay. This the data stream to permit error correc- bytes in a transport stream packet. module delays the three data streams tion in the receiver (Viterbi decoder). The in such a manner as to compensate in code rate can be selected according to The error-protected data stream now advance for subsequent delay differ- the required transmission characteristics passes through a splitter in which the ences. of the system. transport stream packets are divided into up to three hierarchical layers.

FIG 5 ISDB-T channel coding. Splitter Energy Delay Byte wise Convolutional Dispersal Adjustment Interleaving Coding

Outer Code Energy Delay Byte wise Convolutional OFDM Multiplexing RS (204,188) Dispersal Adjustment Interleaving Coding Modulation

Energy Delay Byte wise Convolutional Dispersal Adjustment Interleaving Coding

34 News from Rohde&Schwarz Number 177 (2003/I) Modulation

Bit Interleaving Mapper

Modulation Synthesis of Channel Time Frequency OFDM Guard Hierarchical Coding Bit Interleaving Mapper Interleaver Interleaver Frame IFFT Interval Burst Adaptation Insertion Stream Modulation

Bit Interleaving Mapper

Control Signal FIG 6 Schematic of modulation block with ISDB-T.

Modulation ment interleaver is applied between the tion control (TMCC) as well as auxiliary FIG 6 shows the functional design of OFDM segments that have the same channel (AC) carriers at different posi- the OFDM modulation block with ISDB-T. modulation, followed by an intra-seg- tions in the data stream. The first block performs the modulation, ment interleaver that rotates the data which includes bitwise interleaving with in a segment. The data then passes The generated data is subjected to an delay adjustment and the mapping of through an intra-segment randomizer inverse Fourier transform (IFFT) to trans- the constellation diagram of the modula- that shifts it to quasi-random positions fer it from frequency to time domain. The tion. Possible constellations with ISDB-T within a segment. IFFT length depends on the selected are DQPSK, QPSK, 16QAM and 64QAM. ISDB-T mode and can be 2K, 4K or 8K. The constellation can be selected accord- Frames are formed from 204 OFDM sym- ing to the required transmission charac- bols by adding pilot carriers. Depend- By inserting a guard interval, the OFDM teristics of the system. Suitable bitwise ing on the mode and the selected mod- symbols are extended by a specific interleaving and delay adjustment are ulation, the module adds pilot carriers, factor (1/4, 1/8, 1/16 or 1/32). This has a automatically selected. transmission and multiplexing configura- positive effect on the receiving charac- teristics with . The hierarchical data stream is now syn- thesized. For this purpose, the complex mapped data from each of the three paths is appended end-to-end to form a FIG 7 The R&S SFQ shows all parameters at a glance. serial data stream.

The subsequent symbol-by-symbol time interleaving is performed by an intra- segment time interleaver, whose depth can be set independently for each layer. Delay adjustment is also assigned to the time interleaver in order to compensate for different delays in the paths.

Frequency interleaving then scrambles the data within an OFDM symbol, i.e. at the frequency layer. First, an inter-seg-

35 News from Rohde&Schwarz Number 177 (2003/I) BROADCASTING Test transmitters

Test transmitters from Manual operation of both the R&S SFQ The optional fading simulator for the Rohde&Schwarz for ISDB-T and the R&S SFL test transmitter is very R&S SFQ is ideal for simulating ter- user-friendly. The R&S SFQ features tried- restrial receive conditions, mainly the Rohde & Schwarz offers the new digital and-tested operation via keys, while the reflections in adverse environments and modulation standard in two product fam- R&S SFL provides a practical rollkey. The the inherent motion of a mobile receiver. ilies. The tried-and-tested TV Test Trans- large display on the R&S SFQ (FIG 7) mitter R&S SFQ [3] can be expanded by shows all relevant and easy-to-set oper- The TV Test Transmitter R&S SFL fea- the optional ISDB-T coder (R&S SFQ-B26). ating parameters at a glance. Both tures an optional digital generator, The R&S SFQ is a multistandard device instruments can be remote-controlled allowing the same measurements possi- that is primarily designed for the devel- via the IEC/IEEE bus (IEEE 488) and the ble with the R&S SFQ. opment of set-top boxes. The R&S SFL serial interface (RS-232-C). instrument family already features five A BER option is available for both instru- different models [4] and has now been ments so that the quality of a DUT can expanded by the R&S SFL-I which mainly Possible simulations be evaluated also via the BER. This is an covers production applications. The extremely space-saving solution, since newly developed ISDB-T coder is large- The TV Test Transmitter R&S SFQ pro- no other instruments are required apart scale integrated and, like the other vides a fully standard-compliant RF from the generator. coders of the product family, accom- signal. Moreover, a test transmitter must modated on a single board. The use of be able to simulate real transmission FPGAs allows highly flexible response to conditions. The R&S SFQ is designed as Summary possible modifications or expansions of a stress generator, allowing tests at the the standard. A simple software update specification limits and beyond. The ISDB-T coder underscores the uni- keeps the product family up-to-the- versal expandability of the R&S SFQ, minute. Thus, phase and amplitude of the I/Q which is an instrument that handles modulator can be influenced to simulate all standards and features comprehen- a poorly aligned receive section. Realis- sive means of simulation as required in tic receive conditions can be simulated development, service and quality con- with the aid of a noise generator. Noise trol. The favourably priced R&S SFL with More information and data sheets at www.rohde-schwarz.com power can be precisely set and allows its optional digital noise generator is (search term: SFQ or SFL) the determination of the BER character- just the right choice for production. The istics of ISDB-T receivers. The END point, instruments can always be upgraded a key parameter of a receiver, can also to current developments by installing be determined in this way. software updates.

ATSC Peter Schmidt

TV Test Transmitter SFQ TV Test Transmitter SFL

Digital signals for , satellite and cable Digital signals for use in production

• Wide output frequency range from • Antenna DVB-T • Internal fading simulator ◆ Various optimized models: ◆ Standard-conformant DVB and DTV ◆ For use in production environments: 0.3 MHz to 3300 MHz – 2K and 8K COFDM – 6 or 12 paths – SFL-T for DVB-T standard signals – Wear-free electronic attenuator • Large output level range for transmis- – 6/7/8 MHz bandwidth – Profiles: Constant Phase, Rayleigh, – SFL-V for ATSC/8VSB standard ◆ Wide output frequency range from – Fast setting times sion, receiver and module measure- – Hierarchical coding Rice, Pure Doppler, Log Normal – SFL-J for ITU-T J.83/B standard 5 MHz to 1100 MHz ◆ Flexible input interfaces ◆ ments • Antenna ATSC – Predefined and user-defined pro- ◆ Antenna DVB-T Large output level range for broadcast – SPI • Standard DVB, DTV signals and –8VSB files – 2k and 8k COFDM and receiver measurements – ASI ◆ Operating parameters variable in a FM satellite signals • Cable DVB-C • Internal noise generator for high-pre- – 6 MHz, 7 MHz and 8 MHz – SMPTE310 • Several standards in one unit – Selectable QAM (quadrature am- cision C/N settings wide range – QPSK, 16QAM, 64QAM ◆ I/Q input for external signals • Satellite FM plitude modulation):16, 32, 64, • Internal BER measurement facility for ◆ Internal test signals ◆ Antenna ATSC ◆ Sweep mode for frequency and level – PAL, SECAM, NTSC 128, 256QAM all digital modulation modes (DVB-C, ◆ Special signals and error signals for –8VSB ◆ User-defined correction tables – FM and ADR sound • Satellite DVB-S DVB-S, DVB-T, 8VSB, J.83B) limit testing and troubleshooting ◆ • Flexible input interfaces – Selectable puncturing rate for • Output and input for I/Q signals Cable ITU-T J.83/B –ASI QPSK (quadrature phase shift – 64QAM, 256QAM –SPI keying) – Data interleaver level 1 and level 2 – SMPTE310 • Cable J.83B – Selectable QAM (64, 256 QAM)

Data sheet R&S SFQ Data sheet R&S SFL

REFERENCES Condensed data of the R&S SFQ with optional ISDB-T coder (-B26) [1] ISDB-T standard: ARIB STD-B31 Frequency range 0.3 MHz to 3.3 GHz [2] Overview of ISDB-T specifications: Level range –99 dBm to +4 dBm www..or.jp/strl/open99/de-2/ Data inputs ASI, SPI, TS PARALLEL+AUX shosai-e.html Options coder (for several standards), [3] TV Test Transmitter R&S SFQ: Now signals fading, BER, noise generator, diversity to digital cable standard ITU-T / J.83B. Remote control IEC-625 (IEEE 488) and RS-232-C News from Rohde & Schwarz (2001) No. 170, pp 34–36 Condensed data of the R&S SFL-I [4] TV Test Transmitter R&S SFL – Five Frequency range 5 MHz to 1.1 GHz specialists in production: test sig- Level range –140 dBm to 0 dBm nals for all digital standards. News Data inputs ASI, SPI from Rohde & Schwarz (2001) No. 172, Options BER, digital noise generator pp 30–33 Remote control IEC-625 (IEEE 488) and RS-232-C

36 News from Rohde&Schwarz Number 177 (2003/I)