Receiver and receiving method for hierarchical modulation in single frequency networks

A method of receiving and recovering Orthogonal Frequency Division Multiplexed (OFDM) symbols comprising:

• detecting a radio frequency signal representing a combination of both first and second OFDM symbols, the first and the second OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain and modulated with data symbols being communicated, the second OFDM symbols carrying national broadcast data symbols from a national data pipe and modulated on to the sub-carriers of the second OFDM symbols using a first modulation scheme to form national broadcast modulation symbols, and the first OFDM symbols carrying the national broadcast data symbols from the national data pipe and the local service data symbols from a local insertion pipe and modulated on to the sub-carriers of the first OFDM symbols using a second modulation scheme, the first and the second OFDM symbols both including the same pilot sub-carrier symbols and the first OFDM symbols including local pilot symbols, and forming a received base band signal representing the combined first and second OFDM symbols,
• recovering modulation symbols carrying the local service data symbols from the data bearing sub-carriers of the first OFDM symbols, and
• generating an estimate of the local service data symbols from the modulation symbols carrying the local service data symbols, wherein the recovering the local service modulation symbols comprises
• generating an estimate of a combined channel ([Hn(z)+Hl(z)]) via which the first and second OFDM symbols have passed using the pilot sub-carrier symbols of the first and second OFDM symbols;
• generating an estimate of the national broadcast modulation symbols from the modulated data bearing sub-carriers of the first modulation scheme from the second OFDM symbols (Ŝ(z));
• generating an estimate of a convolution of the combined channel and the national broadcast modulation symbols (Ŝ(z)[Hn(z)+Hl(z)]);
• generating an estimate of a component of the received base band signal representing the local service modulation symbols of the first OFDM symbol by subtracting from the received signal the generated estimate of the national broadcast modulation symbols convolved with the estimate of the combined channel
• (D(z)Hl(z)≈R(z)−Ŝ(z)[Hn(z)+Hl(z)]);
• generating an estimate of a channel via which the first OFDM symbols were received using the local pilot symbols (Ĥl(z));
• generating by circuitry an estimate of local service data symbols from a combination of the estimate of the component of the received signal representing the modulation symbols carrying the local service data and the estimate of the channel via which the first OFDM symbols were received
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A transmitter for communicating data using Orthogonal Frequency Division Multiplexed (OFDM) symbols, the OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain for modulating with the data to be carried and pilot sub-carriers and the transmitter being configured to form a Multiple Input Multiple Output (MIMO) scheme, the transmitter including

• a modulator configured
• to receive on a first input, national broadcast data symbols from a first data pipe according to a national broadcast channel for transmission,
• to receive on a second input, local service data symbols from a local service insertion data pipe according to a local service channel for transmission, and
• to modulate the data bearing sub-carrier signals of the OFDM symbols with either the national broadcast data symbols or the local service data symbols and the national broadcast symbols, the modulation of the data bearing sub-carrier signals of the OFDM symbols with the national broadcast data symbols being performed by mapping the data symbols according to a first modulation scheme, and
• the modulation of the sub-carrier signals of the OFDM symbols with the local service data symbols and the national broadcast data symbols being performed by mapping the national broadcast data symbols and the local service data symbols according to a second modulation scheme,
• a MIMO encoder configured to receive the OFDM symbols and to form at least first and second versions of the OFDM symbols,
• a frequency interleaver configured to receive the first and second versions of the OFDM symbols and to interleave the position of the respective modulated sub-carriers;
• and
• a pilot signal inserter configured to receive the first and second version of the OFDM symbols and to insert first pilot symbols at the pilot sub-carriers of the first version of the OFDM symbols and second pilot symbols at the pilot sub-carriers of the second version of the OFDM symbols;
• a radio frequency modulator configured to modulate a radio frequency carrier signal with the first and second versions of the OFDM symbols for transmission via first and second antennas respectively, wherein
• the first modulation scheme is a lower order modulation scheme providing first modulation symbols with values from a smaller number of constellation points in the complex plane than the second modulation scheme which is a higher order modulation scheme, the second modulation scheme providing second modulation symbols with values which are disposed in the complex plane about corresponding values of the first modulation scheme, with the effect that detection of one of the second modulation symbols of the second modulation scheme will provide the local insertion data symbols and the national broadcast data symbols and allow detection of national broadcast modulation symbols from the first modulation scheme providing the national broadcast data symbols, in the presence of modulation symbols from the second modulation scheme, and if the modulator is configured to modulate the data bearing sub-carriers with both the local service data symbols and the national broadcast symbols, the transmitter is configured
• to generate local pilot symbols at predetermined locations within the first and second OFDM symbols,
• to de-interleave the local pilot symbols from the locations within the first and second OFDM symbols, the de-interleaving being a reverse mapping of the interleaving performed by the frequency interleaver, and
• to include the local pilot symbols with the local service data symbols at the locations determined by the de-interleaving.

A method of transmitting data using Orthogonal Frequency Division Multiplexed (OFDM) symbols, the OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain for modulating with the data to be carried and pilot sub-carriers and arranged to form a Multiple Input Multiple Output (MIMO) scheme, the method including

• receiving on a first input, national broadcast data symbols from a first data pipe according to a national broadcast channel for transmission,
• receiving on a second input, local service data symbols from a local service insertion data pipe according to a local service channel for transmission, and
• modulating the data bearing sub-carrier signals of the OFDM symbols with either the national broadcast data symbols or the local service data symbols and the national broadcast symbols, the modulation of the data bearing sub-carrier signals of the OFDM symbols with the national broadcast data symbols being performed by mapping the data symbols according to a first modulation scheme, and
• the modulation of the sub-carrier signals of the OFDM symbols with the local service data symbols and the national broadcast data symbols being performed by mapping the national broadcast data symbols and the local service data symbols according to a second modulation scheme,
• forming at least first and second versions of the OFDM symbols,
• receiving the first and second versions of the OFDM symbols and interleaving the position of the respective modulated sub-carriers of the first and second versions of the OFDM symbols;
• and
• receiving the interleaved first and second versions of the OFDM symbols and inserting first pilot symbols at the pilot sub-carriers of the first version of the OFDM symbols and second pilot symbols at the pilot sub-carriers of the second version of the OFDM symbols;
• and
• modulating by circuitry a radio frequency carrier signal with the first and second versions of the OFDM symbols for transmission via first and second antennas respectively, wherein
• the first modulation scheme is a lower order modulation scheme providing first modulation symbols with values from a smaller number of constellation points in the complex plane than the second modulation scheme which is a higher order modulation scheme, the second modulation scheme providing second modulation symbols with values which are disposed in the complex plane about corresponding values of the first modulation scheme, with the effect that detection of one of the second modulation symbols of the second modulation scheme will provide the local insertion data symbols and the national broadcast data symbols and allow detection of national broadcast modulation symbols from the first modulation scheme providing the national broadcast data symbols, in the presence of modulation symbols from the second modulation scheme, and the modulating the data bearing sub-carrier signals of the OFDM symbols includes, if the modulating is modulating the data bearing sub-carriers with both the local service data symbols and the national broadcast symbols,
• generating local pilot symbols at predetermined locations within the first and second OFDM symbols,
• de-interleaving the local pilot symbols from the locations within the first and second OFDM symbols, the de-interleaving being a reverse mapping of the interleaving performed by the frequency interleaving, and
• inserting the local pilot symbols with the local service data symbols at the locations determined by the de-interleaving.

A transmitter for communicating data using Orthogonal Frequency Division Multiplexed (OFDM) symbols, the OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain for modulating with the data to be carried and pilot sub-carriers, the transmitter including

• a modulator configured
• to receive on a first input, national broadcast data symbols from a first data pipe according to a national broadcast channel for transmission,
• to receive on a second input, local service data symbols from a local service insertion data pipe according to a local service channel for transmission, and
• to modulate the data bearing sub-carrier signals of the OFDM symbols with either the national broadcast data symbols or the local service data symbols and the national broadcast symbols, the modulation of the data bearing sub-carrier signals of the OFDM symbols with the national broadcast data symbols being performed by mapping the data symbols according to a first modulation scheme, and
• the modulation of the sub-carrier signals of the OFDM symbols with the local service data symbols and the national broadcast data symbols is performed by mapping the national broadcast data symbols and the local service data symbols according to a second modulation scheme, and
• to modulate the pilot sub-carriers of the OFDM symbols with pilot symbols to form the OFDM symbols for transmission;
• a radio frequency modulator which is configured to modulate a radio frequency carrier signal with the OFDM symbols for transmission, wherein
• the first modulation scheme is a lower order modulation scheme providing first modulation symbols with values from a smaller number of constellation points in the complex plane than the second modulation scheme which is a higher order modulation scheme, the second modulation scheme providing second modulation symbols with values which are disposed in the complex plane about corresponding values of the first modulation scheme, with the effect that detection of one of the second modulation symbols of the second modulation scheme will provide the local insertion data symbols and the national broadcast data symbols and allow detection of national broadcast modulation symbols from the first modulation scheme providing the national broadcast data symbols, in the presence of modulation symbols from the second modulation scheme, and if the modulator is configured to modulate the data bearing sub-carriers with both the local service data symbols and the national broadcast symbols, to include local pilot symbols with the local service data symbols.

A method of transmitting data using Orthogonal Frequency Division Multiplexed (OFDM) symbols, the OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain for modulating with the data to be carried and pilot sub-carriers, the method including

• receiving on a first input, national broadcast data symbols from a first data pipe according to a national broadcast channel for transmission,
• receiving on a second input, local service data symbols from a local service insertion data pipe according to a local service channel for transmission, and
• modulating the data bearing sub-carrier signals of the OFDM symbols with either the national broadcast data symbols or the local service data symbols and the national broadcast symbols, the modulating the data bearing sub-carrier signals of the OFDM symbols with the national broadcast data symbols being performed by mapping the data symbols according to a first modulation scheme, and
• the modulating the sub-carrier signals of the OFDM symbols with the local service data symbols and the national broadcast data symbols being performed by mapping the national broadcast data symbols and the local service data symbols according to a second modulation scheme, and
• modulating by circuitry pilot sub-carriers of the OFDM symbols with pilot symbols to form the OFDM symbols for transmission;
• wherein the first modulation scheme is a lower order modulation scheme providing first modulation symbols with values from a smaller number of constellation points in the complex plane than the second modulation scheme which is a higher order modulation scheme, the second modulation scheme providing second modulation symbols with values which are disposed in the complex plane about corresponding values of the first modulation scheme, with the effect that detection of one of the second modulation symbols of the second modulation scheme will provide the local insertion data symbols and the national broadcast data symbols and allow detection of national broadcast modulation symbols from the first modulation scheme providing the national broadcast data symbols, in the presence of modulation symbols from the second modulation scheme, and if the circuitry is configured to modulate the data bearing sub-carriers with both the local service data symbols and the national broadcast symbols, to include local pilot symbols with the local service data symbols.