Claims:1. A system (100) for interactive services for digital video broadcasting, the system comprising:
a receiver configured in a gateway (104), the receiver receives a set of signals pertaining to set of frequency channels from one or more user terminals (106);
an analog to digital converter (ADC) (108) coupled to the receiver, the ADC converts the received set of signals to a digital set of signals; and
a polyphase channelizer (110) coupled to the ADC, the polyphase channelizer configured to:
receive, from the ADC, the digital set of signals pertaining to the set of frequency channels;
process the received digital set of signals by performing any or a combination of down-conversion and down-sampling on the received digital set of signals,
wherein, the processed digital set of signals configured to obtain the desired set of channels at baseband at the required sampling rate.
2. The system as claimed in claim 1, wherein polyphase channelizer (110) comprises 8-channel polyphase channelizer that performs 148 operations per input sample.
3. The system as claimed in claim 2, wherein the polyphase channelizer (110) comprises polyphase filters and phase rotators, the polyphase channelizer (110) operates with network control centre (NCC) (116) on multi-frequency time-division (MF-TDMA) hub receiver.
4. The system as claimed in claim 1, wherein the eight equal bandwidth channels is enabled or disabled based on satellite interactive network configuration provided by NCC (116) in real-time.
5. The system as claimed in claim 4, wherein the set of channels are provided with suppression capabilities to reduce the unwanted computation for the invalid channels.
6. The system as claimed in claim 1, wherein one or more demodulators (112) coupled to the polyphase channelizer (110), wherein the output sampling rates of the set of channels is configured based on the requirement of the one or more demodulators (112).
7. The system as claimed in claim 6, wherein the channel bandwidth configurability is given based on transmitting one or more user terminals bandwidth demand allocated by NCC.
8. The system as claimed in claim 6, wherein a memory mapped interface (114) coupled to the one or more demodulators (112), the memory mapped interface (114) provides instructions configurability and coexist with the NCC.
9. The system as claimed in claim 1, wherein sub-channel bandwidth of the receiver is configured according to return channel satellite terminals (RCST) data rate demand, wherein the RCST data demand is any or a combination of terminal information message-unicast (TIM-U) and terminal information message-broadcast (TIM-B).
10. A method (600) for interactive services for digital video broadcasting, the method comprising:
receiving (602), at a receiver configured in a gateway, a set of signals pertaining to set of frequency channels from one or more user terminals;
converting (604), at an analog to digital converter (ADC), the received set of signals to a digital set of signals, the ADC coupled to the receiver;
receiving (606), at a polyphase channelizer, from the ADC, the digital set of signals pertaining to set of frequency channels, the polyphase channelizer (110) coupled to the ADC; and
processing (608), at the polyphase channelizer, the received digital set of signals by performing any or a combination of down-conversion and down-sampling on the received digital set of signals, wherein, the processed digital set of signals configured to obtain the desired set of channels at baseband at required sampling rate.
, Description:TECHNICAL FIELD
[0001] The present disclosure relates, in general, satellite system, and more specifically, relates to a polyphase filter based digital receive channelizer in MF-TDMA system for interactive satellite services.

BACKGROUND
[0002] An interactive satellite network consists of multiple terminals connected to a centralized hub under the multi-frequency time-division (MF-TDMA) system. Each node is transmitting under an allocated frame in the time-frequency plane. Each frame is constructed using bandwidth time units (BTU) as the basic building block. So, a multi-channel receiver should be facilitated at the hub.
[0003] Few exemplary existing technologies in the field of multi-channel receiver system includes multiple receiver chains of radio frequency (RF), intermediate frequency (IF) and analog to digital converter (ADC) paths. These existing technologies suffer from the limitations of increased hardware complexity, thereby increasing the cost of the system. Cost and performance can be achieved using digital signal processing (DSP) based processing of baseband and low IF signals. Availability of wideband ADCs and high-density field-programmable gate arrays (FPGAs) open a gate for the multi-channel receiver design with reduced hardware complexity thereby making the system cost-effective.
[0004] Therefore, there is a need in the art to provide a means that exhibit cost-effective implementation of receive channelizers for MF-TDMA interactive satellite network hub systems.

OBJECTS OF THE PRESENT DISCLOSURE
[0005] An object of the present disclosure relates, in general, satellite system, and more specifically, relates to a polyphase filter based digital receive channelizer in MF-TDMA system for interactive satellite services.
[0006] Another object of the present disclosure provides a system that eliminates additional interpolation/decimation filters from the receiver path.
[0007] Another object of the present disclosure provides a system that reduces hardware complexity.
[0008] Another object of the present disclosure provides a system that enables suppression capabilities to reduce the unwanted computation for the invalid channels.
[0009] Another object of the present disclosure provides a system that provides configurable output channel sampling rates according to MF-TDMA terminal BTU.
[0010] Another object of the present disclosure provides a system that reduces the design complexity of receiver hub by DSP techniques used for polyphase structure.
[0011] Another object of the present disclosure provides a system that reduces computation complexity and FPGA resource utilization, and provides maximum operations per input sample.
[0012] Yet another object of the present disclosure reduces the cost of the system.

SUMMARY
[0013] The present disclosure relates, in general, satellite system, and more specifically, relates to a polyphase filter based digital receive channelizer in MF-TDMA system for interactive satellite services.
[0014] The present disclosure relates to a unique concept of configurable receive channelizer for multi-frequency time-division multiple-access (MF-TDMA) hub system. The implementation complexity reduces as and when the analog block sets are captured and modelled using digital signal processing (DSP) techniques. The growth in the hardware industries urges the DSP engineers to design the system on digital background. The blend of mathematics and complex hardware paves the way for the development of DSP techniques. The requirement of the multi-channel receiver is identified in frequency division multiplexing (FDM) based systems like MF-TDMA in digital video broadcasting-return channel satellite (DVB-RCS2) protocol over return link. Application of fast Fourier transform (FFT) as phase rotators and different phase profile filter banks helped in easy implementation of channelizer, which provides the configurability over several channels and output channel sampling rate. The channelizer fit at the receiver front-end may perform the down-conversion and down-sampling to put the channel data at the baseband at the required sampling rate. It acts as a single block solution for the multi-channel receiver at the hub to down translate the channels to the number of demodulator chains at the back-end.
[0015] In an aspect, the present disclosure provides a system for interactive services for digital video broadcasting, the system including a receiver configured in a gateway, the receiver receives a set of signals pertaining to set of frequency channels from one or more user terminals, an analog to digital converter (ADC) coupled to the receiver, the ADC converts the received set of signals to a digital set of signals, and a polyphase channelizer coupled to the ADC, the polyphase channelizer configured to receive, from the ADC, the digital set of signals pertaining to set of frequency channels, process the received digital set of signals by performing any or a combination of down-conversion and down-sampling on the received digital set of signals, wherein, the processed digital set of signals configured to obtain the desired set of channels at baseband at required sampling rate.
[0016] In an embodiment, the polyphase channelizer may include 8-channel polyphase channelizer that performs 148 operations per input sample.
[0017] In another embodiment, the polyphase channelizer may include polyphase filters, and phase rotators, the polyphase channelizer operates with network control centre (NCC) on multi-frequency time-division (MF-TDMA) hub receiver.
[0018] In another embodiment, the eight equal bandwidth channels may be enabled or disabled based on satellite interactive network configuration provided by NCC in real-time.
[0019] In another embodiment, the set of channels are provided with suppression capabilities to reduce the unwanted computation for the invalid channels.
[0020] In another embodiment, one or more demodulators coupled to the polyphase channelizer, wherein the output sampling rates of the set of channels is configured based on the requirement of the one or more demodulators.
[0021] In another embodiment, the channel bandwidth configurability is given based on transmitting one or more user terminals bandwidth demand allocated by NCC.
[0022] In another embodiment, a memory mapped interface coupled to the one or more demodulators, the memory mapped interface provides instructions configurability and coexist with the NCC.
[0023] In another embodiment, sub-channel bandwidth of the receiver is configured according to return channel satellite terminals (RCST) data rate demand, wherein the RCST data demand is any or a combination of terminal information message-unicast (TIM-U) and terminal information message-broadcast (TIM-B).
[0024] In an aspect, the present disclosure provides a method for interactive services for digital video broadcasting, the method including receiving, at a receiver configured in a gateway, a set of signals pertaining to set of frequency channels from one or more user terminals, converting , at an analog to digital converter (ADC) coupled to the receiver, the received set of signals to a digital set of signals; and receiving, at a polyphase channelizer, from the ADC, the digital set of signals pertaining to set of frequency channels, the polyphase channelizer coupled to the ADC, processing, at the polyphase channelizer, the received digital set of signals by performing any or a combination of down-conversion and down-sampling on the received digital set of signals, wherein, the processed digital set of signals configured to obtain the desired set of channels at base band at required sampling rate.
[0025] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The following drawings form part of the present specification and are included to further illustrate aspects of the present disclosure. The disclosure may be better understood by reference to the drawings in combination with the detailed description of the specific embodiments presented herein.
[0027] FIG. 1A illustrates an exemplary architecture of MF-TDMA based interactive satellite network system, in accordance with an embodiment of the present disclosure.
[0028] FIG. 1B illustrates an exemplary architecture of receiver channelizer, in accordance with an embodiment of the present disclosure.
[0029] FIG. 2 illustrates an exemplary view of MF-TDMA network plan allocated by NCC, in accordance with an embodiment of the present disclosure.
[0030] FIG. 3 illustrates an exemplary view of input spectrum of FDM signal to be channelized, in accordance with an embodiment of the present disclosure.
[0031] FIG. 4 illustrates a conventional channelizer as a replica of analog prototype.
[0032] FIG. 5 illustrates an exemplary view of polyphase channelizer, in accordance with an embodiment of the present disclosure.
[0033] FIG. 6 illustrates an exemplary flow diagram of a method for interactive services for digital video broadcasting, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
[0034] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. If the specification states a component or feature “may”, “can”, “could”, or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.
[0035] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0036] The present disclosure relates, in general, satellite system, and more specifically, relates to a polyphase filter based digital receive channelizer in multi-frequency time-division multiple-access (MF-TDMA) system for interactive satellite services.
[0037] The present disclosure relates to a unique concept of configurable receive channelizer for MF-TDMA hub system. The implementation complexity reduces as and when the analog block sets are captured and modelled using digital signal processing (DSP) techniques. The growth in the hardware industries urges the DSP engineers to design the system on digital background. The blend of mathematics and complex hardware paves the way for the development of DSP techniques. The requirement of the multi-channel receiver is identified in frequency division multiplexing (FDM) based systems like MF-TDMA in digital video broadcasting-return channel satellite (DVB-RCS2) protocol over return link. Application of fast Fourier transform (FFT) as phase rotators and different phase profile filter banks helped in easy implementation of channelizer, which provides the configurability over several channels and output channel sampling rate. The channelizer fit at the receiver front-end may perform the down-conversion and down-sampling to put the channel data at the baseband at the required sampling rate. It acts as a single block solution for the multi-channel receiver at the hub to down translate the channels to the number of demodulator chains at the back-end.
[0038] The present disclosure is compatible with standard network control centre (NCC) commands as per DVB-RCS2 protocol, configurable channels up to 8 numbers, channel suppression capability, configurable output channel sampling rates according to MF-TDMA terminal BTU, reduced computation complexity and FPGA resource utilization and enables maximum 148 operations per input sample. The present disclosure can be described in enabling detail in the following examples, which may represent more than one embodiment of the present disclosure.
[0039] FIG. 1A illustrates an exemplary architecture of MF-TDMA based interactive satellite network system, in accordance with an embodiment of the present disclosure.
[0040] Referring to FIG. 1A, multi-frequency time-division multiple-access (MF-TDMA) hub system 100 (also referred to as a system 100, herein) configured to broadcast programs via a satellite. The system 100 may include satellite 102 stationed in a geostationary orbit, gateway/hub104 that may be located within each beam of the satellite 102, and one or more user terminals also interchangeably referred to as return channel satellite terminals (RCST) (e.g., 106-1 to 106-n, (which are collectively referred to as one or more user terminals 106, hereinafter) transmits signals to the gateway 104. The system 100 may include a network, such as the Internet, interfaced with the gateway 104 that may be configured to communicate with one or more user terminals 106, via the satellite 102. The system 100 may include digital video broadcasting-return channel satellite (DVB-RCS2) for the uplink signal and digital video broadcasting via satellite (DVB-S2X) for the downlink signal.
[0041] In an embodiment, the gateway 104 may communicate with one or more user terminals 106. The one or more user terminals 106 may interactively communicate back to the gateway 104. The network is based on the MF-TDMA technology in which the hub 104 allocates the centre frequency. One or more networks to which the gateways 104 provide access is connected to a network control centre (NCC), which controls and monitors the configuration of the forward and return paths via the satellite 102, based on predicted traffic requirements.
[0042] In an exemplary embodiment, the present disclosure relates to the cost-effective implementation of receive channelizers for MF-TDMA interactive satellite network hub systems 100 using polyphase filters in hardware involving a wideband analog to digital converters (ADC) and field-programmable gate array (FPGA). The algorithm gives advantages from hardware complexity in designing multiple receive paths and improvement in FPGA resource utilization from conventional network-centric operations (NCO) based digital signal processing (DSP) algorithm.
[0043] FIG. 1B illustrates an exemplary architecture of receiver channelizer, in accordance with an embodiment of the present disclosure.
[0044] In an embodiment, a receiver configured in the gateway 104 operable to receive a set of signals pertaining to set of frequency channels. An ADC 108 configured to convert received set of signals to a digital set of signals. A polyphase channelizer 110 coupled to the ADC 108, the polyphase channelizer 110 may include a polyphase filter, and fast Fourier transform (FFT) processor, where the application of FFT as phase rotators and different phase profile filter banks helped in easy implementation of channelizer 110 which provides the configurability over the number of channels and output channel sampling rate.
[0045] The polyphase channelizer 110 configured to perform down-conversion and down-sampling of the digital set of signals to obtain the desired set of channels (channel data) at the baseband at the required sampling rate. In an exemplary embodiment, the polyphase channelizer 110 may be 8-channel polyphase channelizer that may include the polyphase filter that may be used to down-convert and down-sample the set of channels. The set of channels are being down-converted and down-sampled, appropriate sets of phase rotators can be applied to the filter stage outputs and summed to form each channel output.
[0046] One or more demodulators (e.g., 112-1 to 112-8 (which are collectively referred to as one or more demodulators 112, hereinafter) coupled to polyphase channelizer 110 and operable to receive the digital set of signals from the polyphase channelizer 110 to demodulate the received digital set of signals. The channel output sampling rates can be configured (fractions of ADC_sampling_rate/8) as per the requirement of the demodulator chain at the back end, thereby additional interpolation/decimation filters can be eliminated from the receiver path.
[0047] Advanced Extensible Interface (AXI) bridge 114 also interchangeably referred to as memory-mapped interface 114 coupled to each of the one or more demodulators 112, the AXI bridge coupled to the NCC 116. The memory-mapped interface (AXI4 to the processor system) provides software/instructions configurability during run time and coexists with the NCC client 116 applications. The channelizer 110 works close with NCC client 116 on MF-TDMA hub receiver. The one or more demodulators 112 coupled to the buffer 118. The input and cyclic buffers are given an offset as per the required output channel sampling rate.
[0048] In an exemplary embodiment, the configurable polyphase filter based channelizer with configurable number of channels and channel output sampling rate is implemented as a receiver front end on a hardware consisting of Xilinx Zynq system on a chip (SoC) and AD9364 RF agile transceiver.
[0049] In an implementation, the system 100 for interactive services for digital video broadcasting, the system 100 includes the receiver configured in the gateway 104, the receiver may receive the set of signals pertaining to a set of frequency channels from one or more user terminals 106. The ADC 108 coupled to the receiver, the ADC may convert the received set of signals to the digital set of signals. The polyphase channelizer 110 coupled to the ADC 108, the polyphase channelizer configured to receive, from the ADC 108, the digital set of signals pertaining to set of frequency channels. The polyphase channelizer 110 may process the received digital set of signals by performing any or a combination of down-conversion and down-sampling on the received digital set of signals, where, the processed digital set of signals configured to obtain the desired set of channels at baseband at the required sampling rate.
[0050] For example, the RCST may request service from the gateway, the signal from the RCST is sent to the gateway through the satellite in DVB-RCS2 format. The receiver channelizer in the gateway simultaneously down-convert and down-sample the set of frequency division multiplexed (FDM) channels and downlinks the time-division multiplexing (TDM) channels to the one or more user terminals in DVBS2X format for broadcasting multimedia service signals to the one or more user terminals.
[0051] In an exemplary embodiment, the polyphase channelizer 110 performs 148 operations per input sample. The polyphase channelizer 110 may include polyphase filters and phase rotators. The eight equal bandwidth channels may be enabled or disabled based on satellite interactive network configuration provided by the NCC 116 in real-time. The set of channels may be provided with suppression capabilities to reduce the unwanted computation for the invalid channels. The channel bandwidth configurability is given based on transmitting one or more user terminals 106 bandwidth demand allocated by NCC 116 network plan. The sub-channel bandwidth of the receiver is configured according to RCST data rate demand, where the RCST data demand is any or a combination of terminal information message-unicast (TIM-U) and terminal information message-broadcast (TIM-B). The polyphase channelizer 110 may operate with NCC 116 on MF-TDMA hub receiver.
[0052] Thus, the present disclosure eliminates additional interpolation/decimation filters from the receiver path, reduces hardware complexity, reduces the cost of the system 100 and enables suppression capabilities to reduce the unwanted computation for the invalid channels. The system 100 reduces computation complexity and FPGA resource utilization and provides maximum operations per input sample.
[0053] FIG. 2 illustrates an exemplary view of MF-TDMA network plan allocated by NCC, in accordance with an embodiment of the present disclosure.
[0054] As shown in FIG. 2, one or more networks to which the gateways 104 provide access is connected to NCC 116, which controls the configuration of the physical forward and return paths via the satellite 102, based on predicted traffic requirements. The bandwidth and time slot in which the one or more user terminals 106 send their respective data to form a super-frame. The super-frame is down-converted and down-sampled to retrieve the data sent. Thus, demodulator 112 at the hub should be able to separate the sub-band of the signal and individually recover the data at each sub-band. Receiver sub-channel bandwidth can be configured according to RCST data rate demand such as TIM-U/TIM-B.
[0055] FIG. 3 illustrates an exemplary view of input spectrum of FDM signal to be channelized, in accordance with an embodiment of the present disclosure. As shown in FIG. 3, input signal also interchangeably referred to as the set of signals composed of many equal bandwidth, equally spaced, FDM channels. These channels are digitally down-converted and down-sampled to baseband at the required sampling rate using polyphase channelizer 110.
[0056] FIG. 4 illustrates a conventional channelizer as a replica of analog prototype. As illustrated in FIG. 4, the conventional channelizer process consumes more of the hardware as it requires a pair of the mixers per channel. As the number of channels increase, the hardware complexity and resource utilization increase. Therefore, the hardware complexity and resource utilization may be reduced by using the best possible DSP technique that down-convert and down-sample each channel data. The usage of a 544 tap finite impulse response (FIR) low pass filter with conventional NCO based 8 path channelizer performs 8800 ops per sample. The present disclosure provides bank of filter with different phase profile and phase rotator to bring the channel to the baseband.
[0057] FIG. 5 illustrates an exemplary view of polyphase channelizer, in accordance with an embodiment of the present disclosure
[0058] As shown in FIG.5. the polyphase channelizer 110 may include resampler, all-pass partition, and FFT phase shifters. The polyphase channelizer 110 offers the number of significant advantages compared to conventional channelizer. Application of FFT as phase rotators and different phase profile filter banks helped in easy implementation of channelizer which provides the configurability over the number of channels and output channel sampling rate.
[0059] The architecture of polyphase filter based channelizer serves the purpose as shown in FIG.4. For the increase in the number of channels, the configuration can be done through just changing the filter coefficients and buffer patterns. This also provides the advantage of configuring the output sample rate of the sub-bands. The approach leads to the easy way of decimation which also consumes resource in conventional methods. Polyphase based channelizer 110 at the receiver front-end is always advantageous in terms of configurability and resource utilization.
[0060] The novel fixed point register-transfer level (RTL) implementation involves the design of low pass prototype filter using remez algorithm for constant stop band attenuation. The prototype filter is converted into polyphase filter bank based on the number of channels configured. The different phase profiles and the time delay required for the FFT which act as phase rotator is added by the polyphase filter. The size of the FFT block is decided based on the number of channels. The input and cyclic buffers are given an offset as per the required output channel sampling rate. The computational complexity of the channelizer is based on the number of filter and number of channels configured. The configurability of the number of channels is limited to 8 to fit to the size of the device and output sampling rate should be less than 40 MHz divided by number of channels.
[0061] FIG. 6 illustrates an exemplary flow diagram of a method for interactive services for digital video broadcasting, in accordance with an embodiment of the present disclosure.
[0062] Referring to FIG. 6, at block 602, receiver configured in the gateway receives a set of signals pertaining to set of frequency channels from one or more user terminals. At block 604, the ADC coupled to the receiver, converts the received set of signals to a digital set of signals. At block 606, the polyphase channelizer receives the digital set of signals pertaining to set of frequency channels from the ADC, the polyphase channelizer coupled to the ADC.
[0063] At block 608, the polyphase channelizer process the received digital set of signals by performing any or a combination of down-conversion and down-sampling on the received digital set of signals, where the processed digital set of signals configured to obtain the desired set of channels at base band at the required sampling rate.
[0064] It will be apparent to those skilled in the art that the system 100 of the disclosure may be provided using some or all of the mentioned features and components without departing from the scope of the present disclosure. While various embodiments of the present disclosure have been illustrated and described herein, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

ADVANTAGES OF THE PRESENT DISCLOSURE
[0065] The present disclosure provides a system that eliminates additional interpolation/decimation filters from the receiver path.
[0066] The present disclosure provides a system that reduces hardware complexity.
[0067] The present disclosure provides a system that enables suppression capabilities to reduce the unwanted computation for the invalid channels.
[0068] The present disclosure provides a system that provides configurable output channel sampling rates according to MF-TDMA terminal BTU.
[0069] The present disclosure provides a system that reduces computation complexity and FPGA resource utilization, and provides maximum operations per input sample.
[0070] The present disclosure provides a system reduces the cost of the system.
[0071] The present disclosure provides reduces the design complexity of receiver hub by DSP techniques used for polyphase structure.