Patent Description:
Wired and wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. Some communications systems may be used in the context of secure communications, such as tactical communications. In addition, some communication systems may experience frequency-dependent interference. Such communications systems may be subject to various constraints and challenges.

<CIT> discloses a system and method of utilizing frequency waterfilling and implicit coordination to mitigate signal jamming in Link <NUM> systems. The system and method of utilizing frequency waterfilling for Link <NUM> include updates to both software and firmware. The frequency waterfilling approach for Link <NUM> modifies the process by which data bits are allocated to hops based on an assessment of hops affected by jamming, thus avoiding portions of the spectrum occupied by a jammer.

<CIT> discloses a forming terminal of a time slot data frame compatible with a data chain and a working method of the same. Based on correlation of data redundancy and requirements for communication quality of service, under the condition of constant radio-frequency bandwidth, the terminal can visually and clearly display the formation process of the time slot data frame through the coordination of parts. The received service data is analyzed, and an appropriate encoding, a modulation, a spread spectrum combined technology and a data encapsulation formats are selected, then the combined technical information is mapped to a fine synchronization field stuffing bits for the time slot data frame, so that when the receiving terminal is in the fine synchronization, the encoding, the modulation and the spread spectrum subsequent combined technical information of the subsequent received data are obtained, which can shorten the preprocessing time of the received data, satisfy the requirement of anti-interference, confidentiality, real-time and coverage of the data chain, and further enhance the adaptability of the data chain to future complex environments and improve system throughput.

The described techniques relate to improved methods, systems, devices, and apparatuses that support channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments. Generally, the described techniques provide for transmitting and receiving wideband waveforms when channels of a system bandwidth are unavailable for transmission. The described techniques may include techniques for transmitting a wideband waveform via a spectral band comprising unavailable channel segments. The techniques may include identifying a subset of a plurality of channels of a system bandwidth available for a transmission in a time period, generating a first wideband waveform having a bandwidth determined according to a number of channels in the subset of the plurality of channels, separating the first wideband waveform into a plurality of segments, mapping the plurality of segments to the subset of the plurality of channels of the system bandwidth, combining the mapped plurality of segments to generate a second wideband waveform, and transmitting the second wideband waveform in the time period.

The described techniques may include techniques for receiving a wideband waveform via a spectral band comprising unavailable channel segments. The techniques may include identifying a subset of a plurality of channels of a system bandwidth available for a transmission in a time period, receiving a first wideband waveform in the time period, separating the first wideband waveform into a plurality of waveform segments corresponding to the subset of the plurality of channels, de-mapping the plurality of waveform segments based at least in part on the subset of the plurality of channels, combining the de-mapped plurality of waveform segments to obtain a second wideband waveform, and demodulating the second wideband waveform to obtain a stream of bits.

Wireless communications systems used for secure communications, such as for tactical communications between military entities, may be subject to various constraints and challenges. For example, such communications may be expected to provide a high level of robustness to external tampering, a high level of reliability, etc. The Link <NUM> communication protocol is an example of a tactical data link that may provide various advantages for tactical communications, such as providing a relatively high level of security for transmissions. Link <NUM> was originally developed for tactical airborne air-to-air communications and supports voice communications and limited data communications. The spectrum used by Link <NUM> has been highly regulated, and the protocol was designed to support sparse waveforms that use relatively little spectrum. Tactical data links such as Link <NUM> may operate as primary user (e.g., prioritized over other users), a secondary user (e.g., a lower priority user than at least one other user), or as a tertiary user (e.g., as a user that obtains permission to use spectrum for transmission).

In recent years the use of Link <NUM> has expanded and the risks of jamming and other undesirable interference have increased. Because tactical data links such as Link <NUM> operate on older physical layers and under relatively tight regulation, however, increasing the capacity (e.g., throughput), spectrum efficiency, and security-particularly while maintaining backward compatibility-may be challenging.

Traditional data links may use single-channel transmission. In this case, if a particular transmission channel is jammed or otherwise unavailable for transmission, the transmitter may select a different channel if available. However, in single-channel transmissions, the transmission energy may be concentrated within the channel and may be more easily detectible or jammable.

As described herein, a transmitter may provide better anti-jamming performance, better throughput, and/or better spectrum efficiency by generating a wideband waveform representing the data to be transmitted and mapping the wideband waveform to multiple available channels. In this case, the information may be spread across multiple channels to reduce detectability of the signal, improve transmission quality and throughput, and mitigate the effect of channel jamming.

For example, in some cases, a transmitter used in a system for transmitting wideband waveforms over a tactical data link may receive a stream of bits for transmission (e.g., from a processor in the system), and may generate a wideband waveform based on the stream of bits. In some cases, the system may be configured to transmit wideband waveforms using a system bandwidth that may include or may be partitioned into multiple channels, where each channel may have a predetermined (e.g., the same) channel bandwidth. In some cases, not all of the channels of the system bandwidth may be available for transmission, such as if one or more of the channels are used for other communications or jammed by a malicious entity.

The transmitter may identify a subset of the channels that are available for transmission (e.g., channels that are unused or unjammed, as determined based on the signal power of the channels). The transmitter may separate the first wideband signal into segments, with each segment having the channel bandwidth, and may map the segments to the available channels. The transmitter may combine the mapped segments into a second wideband waveform and transmit the second wideband waveform using the available channels. In this manner, the transmitter may use all of the available channels together and spread the energy across them-that is, the energy of each bit of data may be spread across multiple channels. In this case, jamming a channel may have limited effect on the quality of the transmission, since it may only affect a small part of the energy of transmission associated with the data.

Although the discussion herein focuses on wireless communications using, for example, tactical data links, such techniques may also be used for other wireless or wireline communications. For example, various wireless or wireline communication environments may experience spectral holes that are not available for transmission (e.g., due to impedance mismatching or due to interference). One such example may be digital subscriber line (DSL) communications, however other examples will be apparent to one of skill in the art. Moreover, such techniques may be applied to other types of signals that are transmitted and received, such as radar signals and sonar signals, and may be used in applications such as in hearing aids.

Aspects of the disclosure are initially described in the context of a wireless communications system. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments.

<FIG> illustrates an example of a communication system <NUM> that may employ channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments, according to various aspects of the disclosure. Communication system <NUM> includes devices <NUM> that may be capable of wireless communication using a tactical data link <NUM>. Devices <NUM> may be a handheld device carried by a user, or may be located in a vehicle such as aircraft, tank, ship, or other type of vehicle. Tactical data link <NUM> may support secure communications between devices <NUM> and may include frequency hopping capabilities. Frequency hopping may refer to rapidly switching a carrier among different frequency channels using a sequence (e.g., a pseudorandom sequence) known to both transmitter and receiver. For example, tactical data link <NUM> may support frequency hopping at <NUM> microsecond intervals or at other relatively short intervals.

Tactical data link <NUM> may enable devices <NUM> to communicate on a system bandwidth that includes multiple channels having predetermined bandwidths (e.g., each channel having the same bandwidth). In some cases, not all of the channels may be available for transmission. For example, in some cases tactical data link <NUM> may transmit on a data link network platform having a spectral band (e.g., a system bandwidth) comprising N bandwidth segments (e.g., channels) only M of which may be available at any given time. In some cases, a tactical data link <NUM> may have a spectral band of <NUM> (e.g., a band that ranges from <NUM> to <NUM>), where N is <NUM> channels each comprising <NUM> and M is <NUM> or less.

In some cases, tactical data link <NUM> may be a time division multiple access (TDMA) platform in which each user is assigned one or more time slices in which to transmit. A transmitting user may transmit a message as a sequence of encoded pulses, which are frequency-hopped in a unique hopping pattern among the channels within a time slice. In some cases, each pulse may have a bandwidth equal to a channel bandwidth, and may be mapped to one of the channels according to the hopping pattern. In some cases, the hopping pattern is known to the receiving user. Use of hopping patterns may allow multiple users to transmit in the same time slice. In some cases, each user transmitting in the same time slice but using a different hopping pattern may be referred to as transmitting on a different "net. " In some cases, transmissions may include parallel pulses on each available channel. However, if one or more channels on which the pulses are mapped is jammed or has substantial interference, the link performance may degrade substantially.

According to various aspects of the disclosure, a transmitter may enhance performance over a segmented spectral band by generating a wideband waveform representing the data to be transmitted and mapping the wideband waveform to multiple available channels. Channelizing the wideband waveform may provide better anti-jamming performance, better throughput, and/or better spectrum efficiency. For example, the information may be spread across multiple channels to reduce detectability of the signal, improve transmission quality and throughput, and mitigate the effect of channel jamming.

A transmitter used in a system for transmitting wideband waveforms over a tactical data link may receive a stream of bits for transmission (e.g., from a processor in the system), and may generate a wideband waveform based on the stream of bits. In some cases, the system may be configured to transmit wideband waveforms using a system bandwidth that may include or may be partitioned into multiple channels, where each channel may have a predetermined (e.g., the same) channel bandwidth. In some cases, not all of the channels of the system bandwidth may be available for transmission, such as if one or more of the channels are used for other communications or jammed by a malicious entity.

<FIG> illustrates a system bandwidth <NUM> including <NUM> channels with three devices <NUM> transmitting over three different nets <NUM> of tactical data link <NUM> during a time slice <NUM>. For example, a first device <NUM>-a may transmit over net A <NUM>-a, a second device <NUM>-b may transmit over net B <NUM>-b, and a third device <NUM>-c may transmit over net C <NUM>-c. Each of the devices may concurrently receive or listen to one or more nets <NUM>. For example, device <NUM>-a may transmit over net <NUM>-a while receiving net B <NUM>-b and net C <NUM>-c. Alternatively, some devices <NUM> may only transmit or receive during a given time slice <NUM>. First device <NUM>-a may transmit using three channels <NUM> during each pulse period <NUM> in time slice <NUM>, where the channels <NUM> used by first device <NUM>-a for each pulse period <NUM> of time slice <NUM> may be determined by the hopping pattern associated with net A <NUM>-a. For each time slice <NUM>, device <NUM>-a may determine an available subset of the system bandwidth <NUM>. For example, device <NUM>-a may determine a number of channels that are configured for net A <NUM>-a for time slice <NUM>. Additionally or alternatively, device <NUM>-a may determine a subset of channels <NUM> available for the time slice <NUM>, which may be based on a configuration for the system bandwidth (e.g., for one or more time slices <NUM>). In addition, one or more channels <NUM> may be unavailable due to interference (e.g., jamming). For example, device <NUM>-a may be configured to use three channels <NUM> per pulse period <NUM> of time slice <NUM>, and may determine that <NUM> of the <NUM> channels of the system bandwidth are available for time slice <NUM>. In addition, device <NUM>-a may determine that one or more channels <NUM> have an interference level that meets or exceeds a threshold. In one example, device <NUM>-a may determine that channels <NUM> and <NUM> have excessive interference during time slice <NUM>. Device <NUM>-a may be mapped to different subsets (e.g., provisional subsets) of three channels <NUM> per pulse period <NUM>. For each pulse period <NUM> where net A <NUM>-a is mapped to one or more of channels <NUM> and <NUM>, device <NUM>-a may allocate transmission power to the other channels associated with the pulse period <NUM>. For example, for pulse periods <NUM>, <NUM>, and <NUM> of time slice <NUM>, device <NUM>-a may allocate its transmission power between the other two channels <NUM> (e.g., allocating zero power to channels <NUM> and <NUM>), while in the other pulse periods device <NUM>-a may allocate its transmission power between three channels <NUM>. In some cases, devices <NUM> may make a determination of available channels on a pulse period <NUM> basis. For example, device <NUM>-a may receive or identify an indication of a provisional subset of channels for a given pulse period <NUM>, and may make a determination of the available channels of the provisional subset of channels (e.g., based on interference).

Although illustrated as having <NUM> total channels, tactical data link <NUM> may have any number of channels, and an arbitrary number up to and including all of the total number of channels may be available for each time slice <NUM>. Each net <NUM> may also be associated with varying numbers of channels for each pulse period, up to and including the number of available channels. Although nets A, B, and C are illustrated in <FIG> as having nonoverlapping hopping patterns, hopping patterns for nets <NUM> may overlap during one or more pulse periods <NUM> of a time slice <NUM>, in some cases. Although <FIG> depicts three pulses (e.g., on three channels <NUM>) on each net <NUM> per pulse period <NUM>, in some cases, tactical data link <NUM> may support a different number of pulses on each net <NUM>, such as one pulse per net <NUM> per pulse period <NUM>.

<FIG> illustrates an example of a transmitter <NUM> that supports channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. In some examples, transmitter <NUM> may be included in a wireless communication system, such as wireless communication system <NUM>.

Transmitter <NUM> may be configured to wirelessly transmit wideband waveforms over a tactical data link using one or more antennas <NUM> and a transmitter backend <NUM>. In some cases, a wideband waveform may be a waveform that spans a relatively wide band of frequencies, and may be a spread spectrum waveform Transmitter <NUM> may be configured to transmit wideband waveforms using a system bandwidth, which may be a band of frequencies over which transmitter <NUM> may transmit signals. In some cases, a system bandwidth may be partitioned into channels, with each channel having a respective bandwidth (e.g., the same channel bandwidth). In some cases, one or more channels of the system bandwidth may be unavailable for transmissions if, for example, the channels are excluded from a subset of configured available channels or are jammed by interfering signals (e.g., other transmissions or intentional jamming). In some cases, transmitter <NUM> may identify a channel set <NUM> (e.g., a set of channels selected for transmission) and may transmit wideband waveforms using the channel set <NUM>, as described in more detail herein. In some examples, the channel set <NUM> may correspond to all of the available channels, while in some cases channel set <NUM> may be a subset of the available channels (e.g., a configured number of channels). In some cases channel set <NUM> may be determined by excluding channels from the available channels or configured channels that have a level of signal power (e.g., interference) that satisfies (e.g., meets or exceeds) a threshold.

In operation, transmitter <NUM> may receive a stream of bits <NUM>, such as data bits for transmission. In some cases, the stream of bits <NUM> may be received for transmission in a time period (e.g., a pulse period). In some cases, transmitter <NUM> may receive the stream of bits <NUM> from a processor or other device that is coupled with transmitter <NUM>. Transmitter <NUM> may include a modulator <NUM> for modulating the stream of bits <NUM> to generate a first wideband waveform <NUM>. In some cases, modulator <NUM> may receive an indication of channel set <NUM>, and may modulate the stream of bits <NUM> based on the number of channels in channel set <NUM>. For example, a device that includes transmitter <NUM> may identify a total number of channels of a system bandwidth and a set of available channels for a time slice or pulse period (e.g., configured for the time slice or pulse period, or having a signal power level that does not satisfy a threshold). The device may determine channel set <NUM> from the set of available channels (e.g., a subset or all of the set of available channels).

In some cases, channel set <NUM> may exclude channels that have signal power satisfying the threshold (e.g., due to excessive use or intentional jamming). In some cases, the channel set <NUM> may be non-contiguous; that is, at least two channels in the channel set <NUM> may be separated by one or more channels that are excluded from the channel set <NUM>.

In some cases, the modulator <NUM> may modulate the stream of bits <NUM> to generate a first wideband waveform <NUM> having a bandwidth that is equal to an aggregate bandwidth of the channels in the channel set <NUM>. For example, where the bandwidth of the channels are the same, the bandwidth of first wideband waveform <NUM> may be determined by the number of channels in channel set <NUM> multiplied by the channel bandwidth. In one example, transmitter <NUM> may be configured to transmit via M segments, each segment having a bandwidth of B MHz. Thus, the bandwidth of the first wideband waveform may be equal to M · B MHz. Where the bandwidths of the channels are not the same, the bandwidth of first wideband waveform <NUM> may be determined by summing the bandwidths of the channels in channel set <NUM>.

In some cases, modulator <NUM> may be a variable modulator that may select a modulation scheme (e.g., from a set of modulation schemes) for modulating the stream of bits <NUM> based on various factors. For example, modulator <NUM> may select a modulation scheme based on the channel set <NUM> and/or on a desired coding rate, block error rate (BLER), or throughput. In some cases, the modulation scheme may specify, for example, a modulation type (e.g. BPSK, QPSK, <NUM> QAM, etc.), a type of code (e.g., convolutional code, LDPC code), and a code rate (e.g., a rate <NUM>/<NUM> code, a rate <NUM>/<NUM> code).

Transmitter <NUM> includes analyzer <NUM>. Analyzer <NUM> includes segmenter <NUM> for separating the first wideband waveform <NUM> into multiple segments <NUM>. Segments <NUM> may have respective bandwidths corresponding to channel bandwidths of the channel set <NUM> (e.g., the same bandwidth). In some cases, segmenter <NUM> may separate the first wideband waveform <NUM> into segments <NUM> by applying multiple filters (such as bandpass filters (BPFs)) to the first wideband waveform <NUM>. In some cases, segmenter <NUM> may include a series of filters to separate first wideband waveform <NUM> into segments <NUM>, and may be implemented using a polyphase filter. Each segment <NUM> may have an effective symbol timing that is less (e.g., substantially less) than the symbol timing (e.g., pulse period). That is, each segment <NUM> may carry information associated with multiple symbols in each symbol period or pulse period.

In some cases, analyzer <NUM> includes downconverter <NUM> to downconvert the segments <NUM> to baseband segments <NUM> For example, segments <NUM> may each be associated with different frequency ranges and downconverter <NUM> may downconvert each segment to a baseband frequency range.

Transmitter <NUM> includes mapper <NUM> for mapping the segments (e.g., baseband segments <NUM>) to the corresponding frequency ranges of channel set <NUM>. In some cases, the remaining channels (e.g., channels of the system bandwidth that are not in channel set <NUM>) may be set to null values. For example, mapper <NUM> may output a null segment or null signal for channels of the system bandwidth that are not in channel set <NUM>. A null segment may be a signal having no signal energy within the baseband frequency range.

Mapper <NUM> may map segments <NUM> to channel set <NUM> in an order of the segments <NUM>. Alternatively, mapper <NUM> may scramble an order of the segments <NUM> among channel set <NUM> such that the segments <NUM> are mapped to channel set <NUM> out of order relative to the order of the segments, as depicted in <FIG>. For example, adjacent segments may not be mapped to adjacent channels of channel set <NUM>. Where a scrambled order is used, mapping of non-adjacent segments to adjacent channels of channel set <NUM> may cause aliasing of signal energy from adjacent segments at the receiver. Thus, groups of segments may be mapped to contiguous blocks of channels of channel set <NUM>. That is, groups of contiguous blocks of channel set <NUM> may be identified, and sub-groups of contiguous segments <NUM> may be mapped to each of the groups of contiguous blocks. Mapper <NUM> may output mapped segments <NUM> to synthesizer <NUM>.

In some examples, mapper <NUM> may perform additional processing. For example, mapper <NUM> may perform multipath equalization of segments <NUM> or mapped segments <NUM> before outputting mapped segments <NUM>.

Transmitter <NUM> includes synthesizer <NUM> for generating a second wideband waveform <NUM>. Synthesizer <NUM> includes upconverter <NUM> for upconverting the mapped segments to higher frequencies. Synthesizer <NUM> includes combiner <NUM> for combining the upconverted segments and holes in the spectrum (corresponding to the null values) into a second wideband waveform <NUM> having a bandwidth corresponding to the channel set <NUM> (e.g., extending from a first channel of channel set <NUM> having a lowest frequency to a second channel of channel set <NUM> having a highest frequency). Second wideband waveform <NUM> may have a bandwidth that is wider than first wideband waveform <NUM>. Second wideband waveform may include null frequency ranges (e.g., corresponding to frequency channels of the system bandwidth that are not in channel set <NUM>).

In some cases, by generating the second wideband waveform <NUM> as described herein, the energy of each bit of the stream of bits <NUM> may be spread over the channels in second wideband waveform <NUM> and may therefore be less susceptible to data loss due to jamming of a single channel.

In some cases, transmitter <NUM> may include a transmitter backend <NUM> that includes hardware or software to implement additional processing on second wideband waveform <NUM> before transmission using one or more antennas <NUM>. For example, the second wideband waveform <NUM> may be upconverted to passband before transmission.

In some cases, the transmitted signal (e.g., the transmitted second wideband waveform) will carry the information in the first wideband waveform that is output by the modulator, but there may be substantial energy only in the channels of channel set <NUM>. In this case, the transmitted signal may not interfere with signals transmitted (e.g., by other transmitters) in the other channels of the system bandwidth.

In one example, a system bandwidth of <NUM> may be configured with <NUM> channels (e.g., <NUM> channels). Transmitter <NUM> may identify a channel set <NUM> for a first time period (e.g., a first pulse period) that includes channels <NUM>-<NUM>, <NUM>-<NUM>, <NUM>, and <NUM> (e.g., including <NUM> of the <NUM> channels). Modulator <NUM> may generate a first wideband waveform <NUM> having a bandwidth of <NUM> and analyzer <NUM> may segment and downconvert each segment to generate <NUM> baseband segments <NUM>, each representing a portion (e.g., <NUM>) of the <NUM> bandwidth, and each having a baseband frequency range of <NUM>-<NUM>. Mapper <NUM> may map the baseband segments <NUM> to the channel set <NUM>, and may map null waveforms to channels of the system bandwidth not in channel set <NUM>. Mapper <NUM> may map the baseband segments <NUM> to channel set <NUM> in order, or mapper <NUM> may map the baseband segments <NUM> to channel set <NUM> in a scrambled order. For example, mapper <NUM> may map baseband segment <NUM> to channel <NUM>, baseband segments <NUM>-<NUM> to channels <NUM>-<NUM>, baseband segments <NUM>-<NUM> to channels <NUM>-<NUM>, and baseband segment <NUM> to channel <NUM>. Synthesizer <NUM> may upconvert the mapped segments <NUM> to corresponding frequencies of channel set <NUM> and combine the upconverted segments to obtain a second wideband waveform <NUM>. In this example, second wideband waveform <NUM> may have a bandwidth of <NUM>, with substantially no signal energy in channels <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In instances where channel set <NUM> does not include channel <NUM> or channel <NUM>, second wideband waveform <NUM> may have a bandwidth of less than the system bandwidth of <NUM> (e.g., where one or more segments are not mapped to the upper or lower channels of the system bandwidth).

Transmitter <NUM> may identify a new channel set <NUM> for a second time period (e.g., a second pulse period), and may perform the segmenting, downconverting, mapping, upconverting, and combining to generate a second wideband waveform <NUM> for the second time period. For example, transmitter <NUM> may identify a new channel set <NUM> every pulse period, or every fourth, eighth, or twelfth pulse period, or every time slice, or at some other time period. New channel set <NUM> may be different than the channel set <NUM> for the first pulse period and may or may not have any channels in common with the previous channel set <NUM>. For example, new channel set <NUM> may have the same or a different number of channels. It should be understood that this example is provided for the sake of clarity, and other system bandwidths and channel bandwidths are contemplated without deviating from the scope of the application. For example, the system bandwidth may be <NUM>, and the system may have <NUM> channels where each channel has a <NUM> channel bandwidth. Channel set <NUM> may have up to <NUM> channels in each pulse period and thus first wideband waveform <NUM> may have a bandwidth of up to <NUM> while second wideband waveform <NUM> may have a bandwidth of up to <NUM> (e.g., the system bandwidth).

<FIG> illustrates an example of a portion of a transmitter <NUM> that supports channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. In some examples, transmitter <NUM> may implement aspects of wireless communication system <NUM> or transmitter <NUM>.

Transmitter <NUM> includes analyzer <NUM>-a, mapper <NUM>-a, and synthesizer <NUM>-a, which may be examples of analyzer <NUM>, mapper <NUM>, and synthesizer <NUM> of <FIG>, respectively. A first wideband waveform <NUM>-a may be input to analyzer <NUM>-a. Analyzer <NUM>-a includes multiple bandpass filters <NUM>, downconverters (DCs) <NUM>, and decimators <NUM>. Band-pass filters <NUM> may each be associated with a frequency range of the first wideband waveform <NUM>-a. For example, the first wideband waveform <NUM>-a may have a bandwidth corresponding to an aggregate bandwidth of a number of segments in a channel set <NUM>-a configured for transmission within a pulse period. In one example, transmitter <NUM> may be configured to transmit via M segments, each segment having a bandwidth of B MHz. In this case, analyzer <NUM>-a may have M (or more) bandpass filters <NUM>, each configured to pass a range of frequencies corresponding to the bandwidth of one segment. That is, bandpass filters <NUM> may be configured to pass frequencies in ranges of {<NUM> to B}, {B to 2B},. {(M-<NUM>)*B to M*B}. Bandpass filters <NUM> may output filtered segment waveforms <NUM>.

Downconverters <NUM> may downconvert filtered segment waveforms <NUM> to a baseband frequency range. For example, downconverters <NUM> may downconvert each filtered segment waveform <NUM> to have a frequency range of {<NUM> to B}. Decimators <NUM> may decimate (e.g., downsample) the downconverted filtered segment waveforms <NUM> from a first sample rate associated with the first wideband waveform <NUM>-a to a second, lower sample rate (e.g., which may not cause aliasing because of the smaller bandwidth of each segment). In some cases, bandpass filters <NUM> and downconverters <NUM> may be implemented in a downconverting filter <NUM>. Downconverting filter <NUM> may implement bandpass filters <NUM> using a polyphase filter and an inverse discrete Fourier transform (IDFT). In some cases, both the inputs and the outputs of the inverse DFT are in the time domain. It should be understood that the IDFT may be implemented using an inverse fast Fourier transform (IFFT) algorithm, and the terms IDFT and IFFT may be used interchangeably.

Mapper <NUM>-a may map the downconverted filtered segment waveforms <NUM> to segments of a channel set (e.g., channel set <NUM>-a). Mapper <NUM>-a may map downconverted filtered segment waveforms <NUM> to the segments in order of the downconverted filtered segment waveforms <NUM>. Alternatively, mapper <NUM>-a may map the downconverted filtered segment waveforms <NUM> to the segments of the channel set using a scrambled mapping (e.g., not in order). Mapper <NUM>-a outputs mapped segment waveforms <NUM>, each mapped segment waveform <NUM> being a baseband waveform sampled according to a baseband sampling frequency. Mapper <NUM>-a may output M mapped segment waveforms <NUM>, where M corresponds to a number of segments in channel set <NUM>-a (e.g., null segments may not correspond to a mapped segment waveform <NUM>).

Synthesizer <NUM>-a includes interpolators <NUM>, image rejection (IR) filters <NUM>, upconverters <NUM>, and combiner <NUM>. Interpolators <NUM> effectively upsample the mapped segment waveforms <NUM> by interpolating from the second sample rate to a third, higher sample rate (e.g., a sample rate associated with a system bandwidth). For example, interpolators <NUM> may upsample the mapped segment waveforms <NUM> to a sample rate that is based on an aggregate bandwidth of a total number of channels of the system bandwidth (e.g., a sample rate that satisfies the Nyquist criteria for the system bandwidth).

Image rejection filters <NUM> may perform filtering to suppress image spectra that may result from interpolation.

Upconverters <NUM> upconvert each mapped segment waveform <NUM> to a frequency of the channel set <NUM>-a. For example, a first upconverter <NUM> may upconvert a first mapped segment waveform <NUM> to a frequency of a first channel of the channel set <NUM>-a, a second upconverter <NUM> may upconvert a second mapped segment waveform <NUM> to a frequency of a second channel of the channel set <NUM>-a, and so on, such that each of the mapped segment waveforms <NUM> are upconverted to respective channels of the channel set <NUM>-a. Combiner <NUM> combines the upconverted mapped segment waveforms <NUM> to obtain second wideband waveform <NUM>-a, which may include signal energy in channels of a system bandwidth corresponding to channel set <NUM>-a, and null waveforms (e.g., having substantially no signal energy) in channels of the system bandwidth not within channel set <NUM>-a. Upconverters <NUM> and combiner <NUM> may be implemented as upconverting filter <NUM>. In some cases upconverting filter <NUM> may implement upconverters <NUM> and combiner <NUM> using a polyphase filter and an inverse DFT.

<FIG> illustrates a spectrum plot <NUM> of a channelized wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. Spectrum plot <NUM> shows, for example, a system bandwidth <NUM>-a that includes N channels <NUM>-a. Each channel <NUM>-a may have a channel bandwidth <NUM>. Although <FIG> illustrates channels <NUM>-a having the same channel bandwidth <NUM>, channels <NUM>-a may have different bandwidths, in some cases. In some examples, implementations using a polyphase synthesis bank or a polyphase analysis bank may be applied in environments where each channel <NUM> has the same channel bandwidth <NUM>-a, or are multiples of a power of two.

Spectrum plot <NUM> illustrates spectrum of a second wideband waveform <NUM>-b, which may be generated, for example, by the transmitters <NUM> or <NUM> of <FIG> or <FIG>. Second wideband waveform <NUM>-b may include signal power within channels <NUM>-a of a channel set, while channels that are not included in the channel set may not have substantial signal power (e.g., may have null waveforms). For example, <FIG> illustrates that second wideband waveform <NUM>-b has signal power in channels <NUM>, <NUM>, <NUM>, and N (with some channels not shown for the sake of clarity), while channels <NUM>, <NUM>, and <NUM> have null signals (e.g., substantially no signal power). The bandwidth of the signal power of second wideband waveform <NUM>-b for each channel <NUM>-a may be understood as the range of the spectral density of the channel <NUM>-a that includes signal power over a threshold (e.g., <NUM> dB, <NUM> dB). In some cases, the signal power waveform for each segment may have a guardband (e.g., a segment of <NUM> may have guardbands of <NUM>, or a <NUM> dB bandwidth of <NUM>).

<FIG> illustrate examples of polyphase analysis bank <NUM> and a polyphase synthesis bank <NUM> that support channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. In some examples, polyphase analysis bank <NUM> and polyphase synthesis bank <NUM> may implement aspects of wireless communication system <NUM>.

Polyphase analysis bank <NUM> includes multiple polyphase filters. For example polyphase analysis bank <NUM> is illustrated with P subfilters <NUM> and IDFT <NUM>. Each subfilter <NUM> may have the same or different orders, and may be a bandpass filter. An input signal <NUM> (e.g., first wideband waveform <NUM>) may be input to subfilters <NUM> (e.g., different sample interlaces may be input to subfilters <NUM> by commutator <NUM>) and the output of the subfilters <NUM> may be input to inverse DFT <NUM>. Each subfilter <NUM> may receive an interlaced subset of samples of the input signal <NUM>. For example, subfilters <NUM>-a, <NUM>-b, and <NUM>-c may each receive different subsets of samples of the input signal <NUM>. In some cases, commutator <NUM>, subfilters <NUM>, and IDFT <NUM> may implement a downconversion polyphase filter that outputs downconverted filtered waveform segments <NUM>. For example, commutator <NUM> may downsample the input signal <NUM>, subfilters <NUM> may perform filtering, and IDFT <NUM> may perform downconversion. Polyphase analysis bank <NUM> may be an example of a downconverting filter <NUM>.

Polyphase synthesis bank <NUM> may also include multiple polyphase filters. For example polyphase synthesis bank <NUM> is illustrated with IDFT <NUM> and Q subfilters <NUM>. Each subfilter <NUM> (e.g., subfilters <NUM>-d, <NUM>-e, <NUM>-f and others) may have the same or different orders. Inverse DFT <NUM> may receive Q input signals (e.g., mapped segments <NUM>) and output Q signals to subfilters <NUM>. IDFT <NUM> and subfilters <NUM> may perform filtering and upconversion to generate an upconverted waveform combining the signal energy within the Q signals (e.g., corresponding to Q segments). For example, the output of subfilters <NUM> may be combined by commutator <NUM> (e.g., by interlacing samples from the Q subfilters) to obtain the upconverted waveform (e.g., second wideband waveform <NUM>). That is, IDFT <NUM> may perform upconversion, subfilters <NUM> may perform image reject filtering, and commutator <NUM> may perform upsampling. Polyphase synthesis bank <NUM> may be an example of an upconverting filter <NUM>.

<FIG> illustrates an example of a receiver <NUM> that supports channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. In some examples, receiver <NUM> may be included in a wireless communication system, such as wireless communication system <NUM>.

Receiver <NUM> may be configured to wirelessly receive wideband waveforms over a tactical data link using one or more antennas <NUM>. Receiver <NUM> may be configured to receive a first wideband waveform <NUM> via a system bandwidth, which may be a band of frequencies over which receiver <NUM> may receive signals. In some cases, a system bandwidth may be partitioned into channels, with each channel having a respective bandwidth (e.g., the same channel bandwidth).

In some cases, one or more channels of the system bandwidth of the first wideband waveform <NUM> may be unused for a received signal (e.g., via a "net" of a tactical data link). Unused channels of the system bandwidth may not include data to be received and/or may have a received level of signal power (e.g., signal energy) that is below a threshold. That is, in some cases, there may be substantial energy of the received signal only in a subset of channels of the channels of the system bandwidth. In some cases, the subset of channels may be non-contiguous; that is, at least two channels in the subset of channels may be separated by one or more channels that are excluded from the subset of channels. In some cases, receiver <NUM> identifies that a level of signal power for at least one of the channels of the system bandwidth satisfies a threshold (e.g., is below a minimum), and excludes such channel(s) from the subset of channels <NUM>. Receiver <NUM> may identify or receive an indication of the subset of channels of the system bandwidth associated with a signal for reception (e.g., channel set <NUM>).

In some cases, receiver <NUM> may include a receiver frontend <NUM> that includes hardware or software to process a signal received using antenna(s) <NUM> to generate first wideband waveform <NUM>. For example, receiver frontend <NUM> may filter the received signal, mix the signal (e.g., downconvert), perform analog-to-digital conversion, and/or perform other processing.

Receiver <NUM> includes analyzer <NUM>. Analyzer <NUM> includes segmenter <NUM> for separating the first wideband waveform <NUM> into multiple segments <NUM>. Segments <NUM> may have respective bandwidths corresponding to channel bandwidths of the channels of the system bandwidth (e.g., the same bandwidth). In some cases, segmenter <NUM> may separate the first wideband waveform <NUM> into segments <NUM> by applying multiple filters (such as BPFs) to the first wideband waveform <NUM>. In some cases, segmenter <NUM> may include a series of filters to separate first wideband waveform <NUM> into segments <NUM>, and may be implemented using a downconverting filter. For example, analyzer <NUM> may be structurally similar to analyzer <NUM>-a, downconverting filter <NUM>, or polyphase analysis bank <NUM>. In one example, analyzer <NUM> may be structurally similar to analyzer <NUM>-a with M (or more) bandpass filters <NUM>, where M is the number of channels in channel set <NUM>. Alternatively, analyzer <NUM> may include N (or more) bandpass filters <NUM>, where N is the total number of channels of the system bandwidth.

In some cases, analyzer <NUM> includes downconverter <NUM> to downconvert the segments <NUM> to baseband segments <NUM>. For example, segments <NUM> may each be associated with different frequency ranges and downconverter <NUM> may downconvert each segment <NUM> to a baseband frequency range.

Receiver <NUM> includes mapper <NUM> for de-mapping the segments (e.g., baseband segments <NUM>) corresponding to the channel set <NUM> to the corresponding frequency ranges of synthesizer channels <NUM>. In some cases, the remaining channels (e.g., channels of the system bandwidth that are not included in channel set <NUM>) may be ignored. For example, the system bandwidth may include N channels while channel set <NUM> may include M channels. Mapper <NUM> may map M channels of the N channels that are in channel set <NUM> to a first set of M synthesizer channels <NUM> while N-M channels of synthesizer channels <NUM> may not be mapped (e.g., may have a null signal mapped). In some cases, de-mapping the segments may include de-scrambling an order of the segments according to a scrambling sequence. The scrambling sequence may include an indication of a scrambled order of the segments. In some cases, the scrambling sequence includes multiple sub-groups of the waveform segments, and the sub-groups are de-mapped from respective contiguous blocks of the subset of the plurality of channels.

In some examples, mapper <NUM> may perform additional processing. For example, mapper <NUM> may perform multipath equalization of baseband segments <NUM> before de-mapping the baseband segments <NUM>.

Receiver <NUM> includes synthesizer <NUM> for generating a second wideband waveform <NUM>. Second wideband waveform <NUM> may have a bandwidth that is narrower than first wideband waveform <NUM>. Synthesizer <NUM> includes upconverter <NUM> for upconverting the de-mapped segments <NUM> to higher frequencies. Synthesizer <NUM> includes combiner <NUM> for combining the upconverted de-mapped segments to obtain a second wideband waveform <NUM> having a bandwidth corresponding to the total (e.g., aggregate) bandwidth of channel set <NUM>. In some examples, synthesizer <NUM> may be structurally similar to synthesizer <NUM>-a, upconverting filter <NUM>, or polyphase synthesis bank <NUM>. In one example, synthesizer <NUM> may be structurally similar to synthesizer <NUM>-a with M (or more) interpolators <NUM>, image rejection filters <NUM>, and upconverters <NUM>, where M is the number of channels in the channel set <NUM>.

In some cases, receiver <NUM> may include hardware or software to implement additional processing on second wideband waveform <NUM> to generate a stream of bits <NUM> representing second wideband waveform <NUM>. For example, receiver <NUM> may include a demodulator <NUM> to demodulate second wideband waveform <NUM> to obtain the stream of bits <NUM>. In some cases, a receiver <NUM> may identify a modulation scheme (e.g., from a set of modulation schemes) for demodulating the second wideband waveform <NUM> to obtain stream of bits <NUM> based on information associated with the signal (e.g., from the transmitter). Receiver <NUM> may demodulate the second wideband waveform according to the selected modulation scheme.

Receiver <NUM> may provide the stream of bits <NUM> to a processor or other device that is coupled with receiver <NUM>.

In one example, a system bandwidth of <NUM> may be configured with <NUM> channels (e.g., <NUM> channels). Receiver <NUM> may identify a channel set <NUM> for a first time period (e.g., a first pulse period) that includes channels <NUM>-<NUM>, <NUM>-<NUM>, <NUM>, and <NUM> (e.g., including <NUM> of the <NUM> channels). Receiver <NUM> may receive a first wideband waveform <NUM> (e.g., via antenna(s) <NUM> and receiver frontend <NUM>). The first wideband waveform <NUM> may have a bandwidth corresponding to the system bandwidth (e.g., <NUM>) with substantially no signal energy (e.g., associated with the signal to be received) in channels <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Analyzer <NUM> may segment and downconvert each segment to generate <NUM> baseband segments <NUM>, each representing a portion (e.g., <NUM>) of the <NUM> bandwidth, and each having a baseband frequency range of <NUM>-<NUM>. Mapper <NUM> may map the baseband segments <NUM> corresponding to channel set <NUM> to (e.g., a first <NUM>) synthesizer channels <NUM>, and may map null waveforms to other synthesizer channels <NUM> (e.g., synthesizer channels <NUM> other than the first <NUM>). Mapper <NUM> may map the baseband segments <NUM> from analyzer <NUM> in order, or mapper <NUM> may map the baseband segments <NUM> in a scrambled order. For example, mapper <NUM> may map baseband segments <NUM>-<NUM> to synthesizer channels <NUM>-<NUM>, baseband segments <NUM>-<NUM> to synthesizer channels <NUM>-<NUM>, baseband segment <NUM> to synthesizer channel <NUM>, and baseband segment <NUM> to synthesizer channel <NUM>. Synthesizer <NUM> may upconvert the mapped segments to frequencies corresponding to a width of channels of the system bandwidth and combine the upconverted segments to obtain a second wideband waveform <NUM>. In this example, second wideband waveform <NUM> may have a bandwidth of <NUM>.

Receiver <NUM> may identify a new channel set <NUM> for a second time period (e.g., a second pulse period), and may perform the segmenting, downconverting, mapping, upconverting, and combining to generate a second wideband waveform <NUM> for the second time period. New channel set <NUM> may be different than the channel set <NUM> for the first pulse period and may or may not have any channels in common with the previous channel set <NUM>. For example, new channel set <NUM> may have the same or a different number of channels. It should be understood that this example is provided for the sake of clarity, and other system bandwidths and channel bandwidths are contemplated without deviating from the scope of the application. For example, the system bandwidth may be <NUM>, and the system may have <NUM> channels where each channel has a <NUM> channel bandwidth. Channel set <NUM> may have up to <NUM> channels in each pulse period and thus first wideband waveform <NUM> may have a bandwidth of up to <NUM> while second wideband waveform <NUM> may have a bandwidth of up to <NUM> (e.g., the system bandwidth).

<FIG> shows a diagram of a system <NUM> including a device <NUM> that supports channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. The device <NUM> may include components for bi-directional communications of wideband waveforms including components for transmitting and receiving communications, including a processor <NUM>, an I/O controller <NUM>, a transceiver <NUM>, an antenna <NUM>, and memory <NUM>. These components may be in electronic communication via one or more buses (e.g., bus <NUM>).

The processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (e.g., memory <NUM>) to cause the device <NUM> to perform various functions (e.g., functions or tasks supporting channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments).

The transceiver <NUM> may also include a modem to modulate signals and provide the modulated signals to the antennas for transmission, and to demodulate signals received from the antennas.

However, in some cases the device <NUM> may have more than one antenna <NUM>, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory <NUM> may include RAM and ROM.

The device <NUM> may include channel manager <NUM>. Channel manager <NUM> may identify a subset (e.g., channel set <NUM> or <NUM>) of channels of a system bandwidth available for a transmission in a time period. Each of the channels may have a respective channel bandwidth (e.g., the same channel bandwidth, or different channel bandwidths). The subset of the channels may be non-contiguous. In some examples, the subset of the channels may correspond to all of a set of available channels (e.g., a configured set of available channels, which may be a subset of the total channels of the system bandwidth). Alternatively, the subset of the channels may be a subset of the available channels (e.g., a configured number of channels). In some cases the subset of channels may be determined by excluding channels from the available channels or configured channels that have a level of signal power (e.g., interference) that satisfies (e.g., meets or exceeds) a threshold.

The code <NUM> may include instructions to implement aspects of the present disclosure, including instructions to support methods for transmitting and/or receiving channelized wideband waveforms as described herein. For example, the code <NUM> may include instructions for performing (e.g., by the processor <NUM> and/or the transceiver <NUM>) the functions of the modulator <NUM>, the analyzer <NUM> or <NUM>, the mapper <NUM> or <NUM>, the synthesizer <NUM> or <NUM>, and/or the demodulator <NUM>.

<FIG> shows a flowchart illustrating a method <NUM> that supports channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by a transmitter or a device or their components as described herein. For example, the operations of method <NUM> may be performed by a transmitter as described with reference to <FIG> and/or a device as described with reference to <FIG>. In some examples, a processor may execute a set of instructions to control the functional elements of the default to perform the functions described below. Additionally or alternatively, a transmitter may perform aspects of the functions described below using special-purpose hardware, programmable logic, or other means.

At <NUM>, the transmitter may identify a subset of a set of channels of a system bandwidth available for a transmission in a time period (e.g., channel set <NUM>), where the subset of the set of channels is non-contiguous, and where each of the set of channels has a respective channel bandwidth. For example, each of the set of channels may have the same bandwidth, or some channels of the set of channels may have different bandwidths from other channels. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a transmitter as described with reference to <FIG>.

At <NUM>, the transmitter may generate a first wideband waveform having a bandwidth determined according to a number of channels in the subset of the set of channels. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a transmitter as described with reference to <FIG>.

At <NUM>, the transmitter may separate the first wideband waveform into a set of segments, each segment of the set of segments having a bandwidth corresponding to the respective bandwidth of the channel of the set of channels. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a transmitter as described with reference to <FIG>.

At <NUM>, the transmitter may map the set of segments to the subset of the set of channels of the system bandwidth. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a transmitter as described with reference to <FIG>.

At <NUM>, the transmitter may combine the mapped set of segments to generate a second wideband waveform. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a transmitter as described with reference to <FIG>.

At <NUM>, the transmitter may transmit the second wideband waveform in the time period. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a transmitter as described with reference to <FIG>.

<FIG> shows a flowchart illustrating a method <NUM> that supports channelizing a wideband waveform for transmission on a spectral band comprising unavailable channel segments in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by a receiver or a device or their components as described herein. For example, the operations of method <NUM> may be performed by a receiver as described with reference to <FIG> and/or a device as described with reference to <FIG>. In some examples, a processor may execute a set of instructions to perform the functions described below. Additionally or alternatively, a receiver may perform aspects of the functions described below using special-purpose hardware or programmable logic.

At <NUM>, a receiver may identify a subset of a set of channels of a system bandwidth available for a transmission in a time period, where the subset of the set of channels is non-contiguous, and where each of the set of channels has a same channel bandwidth. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a receiver or device as described with reference to <FIG> and <FIG>.

At <NUM>, the receiver may receive a first wideband waveform in the time period. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a receiver or device as described with reference to <FIG> and <FIG>.

At <NUM>, the receiver may separate the first wideband waveform into a set of waveform segments corresponding to the subset of the set of channels. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a receiver or device as described with reference to <FIG> and <FIG>.

At <NUM>, the receiver may de-map the set of waveform segments based on the subset of the set of channels. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a receiver or device as described with reference to <FIG> and <FIG>.

At <NUM>, the receiver may combine the de-mapped set of waveform segments to obtain a second wideband waveform. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a receiver or device as described with reference to <FIG> and <FIG>.

At <NUM>, the receiver may demodulate the second wideband waveform to obtain a stream of bits. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a receiver or device as described with reference to <FIG> and <FIG>.

By way of example, and not limitation, non-transitory computer-readable media may include random-access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

As used herein, including in the claims, "or" as used in a list of items (e.g., a list of items prefaced by a phrase such as "at least one of" or "one or more of') indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Claim 1:
A method for secure communications, comprising:
identifying a subset of a plurality of channels (<NUM>) of a system bandwidth (<NUM>) available for a transmission in a time period (<NUM>; <NUM>), wherein the subset of the plurality of channels is non-contiguous, and wherein each of the plurality of channels has a respective channel bandwidth;
generating a first wideband waveform (<NUM>) having a bandwidth determined according to a number of channels in the subset of the plurality of channels;
separating the first wideband waveform into a plurality of segments (<NUM>), each segment of the plurality of segments having a bandwidth corresponding to the respective channel bandwidth of a corresponding one of the subset of the plurality of channels;
mapping the plurality of segments to the subset of the plurality of channels of the system bandwidth;
combining the mapped plurality of segments to generate a second wideband waveform (<NUM>); and
transmitting the second wideband waveform in the time period.