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| virtual void | update_gains ()=0 |
| | update the system gains from omega and eta More...
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| virtual void | set_taps (const std::vector< float > &taps, std::vector< std::vector< float > > &ourtaps, std::vector< gr::filter::kernel::fir_filter_ccf * > &ourfilter)=0 |
| |
virtual std::vector
< std::vector< float > > | taps () const =0 |
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virtual std::vector
< std::vector< float > > | diff_taps () const =0 |
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| virtual std::vector< float > | channel_taps (int channel) const =0 |
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| virtual std::vector< float > | diff_channel_taps (int channel) const =0 |
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| virtual std::string | taps_as_string () const =0 |
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| virtual std::string | diff_taps_as_string () const =0 |
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| virtual void | set_loop_bandwidth (float bw)=0 |
| | Set the loop bandwidth. More...
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| |
| virtual void | set_damping_factor (float df)=0 |
| | Set the loop damping factor. More...
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| virtual void | set_alpha (float alpha)=0 |
| | Set the loop gain alpha. More...
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| virtual void | set_beta (float beta)=0 |
| | Set the loop gain beta. More...
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| virtual void | set_max_rate_deviation (float m)=0 |
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| virtual float | loop_bandwidth () const =0 |
| | Returns the loop bandwidth. More...
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| virtual float | damping_factor () const =0 |
| | Returns the loop damping factor. More...
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| virtual float | alpha () const =0 |
| | Returns the loop gain alpha. More...
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| virtual float | beta () const =0 |
| | Returns the loop gain beta. More...
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| |
| virtual float | clock_rate () const =0 |
| | Returns the current clock rate. More...
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| |
| virtual float | error () const =0 |
| | Returns the current error of the control loop. More...
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| |
| virtual float | rate () const =0 |
| | Returns the current rate of the control loop. More...
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| virtual float | phase () const =0 |
| | Returns the current phase arm of the control loop. More...
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| virtual | ~block () |
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| unsigned | history () const |
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| void | set_history (unsigned history) |
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| void | declare_sample_delay (int which, unsigned delay) |
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| void | declare_sample_delay (unsigned delay) |
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| unsigned | sample_delay (int which) const |
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| bool | fixed_rate () const |
| | Return true if this block has a fixed input to output rate. More...
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| virtual void | forecast (int noutput_items, gr_vector_int &ninput_items_required) |
| | Estimate input requirements given output request. More...
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| virtual int | general_work (int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) |
| | compute output items from input items More...
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| |
| virtual bool | start () |
| | Called to enable drivers, etc for i/o devices. More...
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| virtual bool | stop () |
| | Called to disable drivers, etc for i/o devices. More...
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| void | set_output_multiple (int multiple) |
| | Constrain the noutput_items argument passed to forecast and general_work. More...
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| int | output_multiple () const |
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| bool | output_multiple_set () const |
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| void | set_alignment (int multiple) |
| | Constrains buffers to work on a set item alignment (for SIMD) More...
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| int | alignment () const |
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| void | set_unaligned (int na) |
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| int | unaligned () const |
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| void | set_is_unaligned (bool u) |
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| bool | is_unaligned () const |
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| void | consume (int which_input, int how_many_items) |
| | Tell the scheduler how_many_items of input stream which_input were consumed. More...
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| void | consume_each (int how_many_items) |
| | Tell the scheduler how_many_items were consumed on each input stream. More...
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| void | produce (int which_output, int how_many_items) |
| | Tell the scheduler how_many_items were produced on output stream which_output. More...
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| void | set_relative_rate (double relative_rate) |
| | Set the approximate output rate / input rate. More...
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| double | relative_rate () const |
| | return the approximate output rate / input rate More...
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| |
| virtual int | fixed_rate_ninput_to_noutput (int ninput) |
| | Given ninput samples, return number of output samples that will be produced. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this. More...
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| |
| virtual int | fixed_rate_noutput_to_ninput (int noutput) |
| | Given noutput samples, return number of input samples required to produce noutput. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this. More...
|
| |
| uint64_t | nitems_read (unsigned int which_input) |
| | Return the number of items read on input stream which_input. More...
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| uint64_t | nitems_written (unsigned int which_output) |
| | Return the number of items written on output stream which_output. More...
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| tag_propagation_policy_t | tag_propagation_policy () |
| | Asks for the policy used by the scheduler to moved tags downstream. More...
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| void | set_tag_propagation_policy (tag_propagation_policy_t p) |
| | Set the policy by the scheduler to determine how tags are moved downstream. More...
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| int | min_noutput_items () const |
| | Return the minimum number of output items this block can produce during a call to work. More...
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| |
| void | set_min_noutput_items (int m) |
| | Set the minimum number of output items this block can produce during a call to work. More...
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| int | max_noutput_items () |
| | Return the maximum number of output items this block will handle during a call to work. More...
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| void | set_max_noutput_items (int m) |
| | Set the maximum number of output items this block will handle during a call to work. More...
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| void | unset_max_noutput_items () |
| | Clear the switch for using the max_noutput_items value of this block. More...
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| bool | is_set_max_noutput_items () |
| | Ask the block if the flag is or is not set to use the internal value of max_noutput_items during a call to work. More...
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| void | expand_minmax_buffer (int port) |
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| long | max_output_buffer (size_t i) |
| | Returns max buffer size on output port i. More...
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| void | set_max_output_buffer (long max_output_buffer) |
| | Sets max buffer size on all output ports. More...
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| |
| void | set_max_output_buffer (int port, long max_output_buffer) |
| | Sets max buffer size on output port port. More...
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| long | min_output_buffer (size_t i) |
| | Returns min buffer size on output port i. More...
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| void | set_min_output_buffer (long min_output_buffer) |
| | Sets min buffer size on all output ports. More...
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| void | set_min_output_buffer (int port, long min_output_buffer) |
| | Sets min buffer size on output port port. More...
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| float | pc_noutput_items () |
| | Gets instantaneous noutput_items performance counter. More...
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| float | pc_noutput_items_avg () |
| | Gets average noutput_items performance counter. More...
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| float | pc_noutput_items_var () |
| | Gets variance of noutput_items performance counter. More...
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| float | pc_nproduced () |
| | Gets instantaneous num items produced performance counter. More...
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| float | pc_nproduced_avg () |
| | Gets average num items produced performance counter. More...
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| float | pc_nproduced_var () |
| | Gets variance of num items produced performance counter. More...
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| float | pc_input_buffers_full (int which) |
| | Gets instantaneous fullness of which input buffer. More...
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| float | pc_input_buffers_full_avg (int which) |
| | Gets average fullness of which input buffer. More...
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| float | pc_input_buffers_full_var (int which) |
| | Gets variance of fullness of which input buffer. More...
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| std::vector< float > | pc_input_buffers_full () |
| | Gets instantaneous fullness of all input buffers. More...
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| std::vector< float > | pc_input_buffers_full_avg () |
| | Gets average fullness of all input buffers. More...
|
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| std::vector< float > | pc_input_buffers_full_var () |
| | Gets variance of fullness of all input buffers. More...
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| float | pc_output_buffers_full (int which) |
| | Gets instantaneous fullness of which input buffer. More...
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| float | pc_output_buffers_full_avg (int which) |
| | Gets average fullness of which input buffer. More...
|
| |
| float | pc_output_buffers_full_var (int which) |
| | Gets variance of fullness of which input buffer. More...
|
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| std::vector< float > | pc_output_buffers_full () |
| | Gets instantaneous fullness of all output buffers. More...
|
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| std::vector< float > | pc_output_buffers_full_avg () |
| | Gets average fullness of all output buffers. More...
|
| |
| std::vector< float > | pc_output_buffers_full_var () |
| | Gets variance of fullness of all output buffers. More...
|
| |
| float | pc_work_time () |
| | Gets instantaneous clock cycles spent in work. More...
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| |
| float | pc_work_time_avg () |
| | Gets average clock cycles spent in work. More...
|
| |
| float | pc_work_time_var () |
| | Gets average clock cycles spent in work. More...
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| |
| float | pc_work_time_total () |
| | Gets total clock cycles spent in work. More...
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| |
| void | reset_perf_counters () |
| | Resets the performance counters. More...
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| |
| void | setup_pc_rpc () |
| | Sets up export of perf. counters to ControlPort. Only called by the scheduler. More...
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| bool | is_pc_rpc_set () |
| | Checks if this block is already exporting perf. counters to ControlPort. More...
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| void | no_pc_rpc () |
| | If the block calls this in its constructor, it's perf. counters will not be exported. More...
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| |
| void | set_processor_affinity (const std::vector< int > &mask) |
| | Set the thread's affinity to processor core n. More...
|
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| void | unset_processor_affinity () |
| | Remove processor affinity to a specific core. More...
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| std::vector< int > | processor_affinity () |
| | Get the current processor affinity. More...
|
| |
| int | active_thread_priority () |
| | Get the current thread priority in use. More...
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| int | thread_priority () |
| | Get the current thread priority stored. More...
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| |
| int | set_thread_priority (int priority) |
| | Set the current thread priority. More...
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| bool | update_rate () const |
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| block_detail_sptr | detail () const |
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| void | set_detail (block_detail_sptr detail) |
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| pmt::pmt_t | message_subscribers (pmt::pmt_t port) |
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| virtual | ~basic_block () |
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| long | unique_id () const |
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| long | symbolic_id () const |
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| std::string | name () const |
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| std::string | symbol_name () const |
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| gr::io_signature::sptr | input_signature () const |
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| gr::io_signature::sptr | output_signature () const |
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| basic_block_sptr | to_basic_block () |
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| bool | alias_set () |
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| std::string | alias () |
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| pmt::pmt_t | alias_pmt () |
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| void | set_block_alias (std::string name) |
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| void | message_port_register_in (pmt::pmt_t port_id) |
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| void | message_port_register_out (pmt::pmt_t port_id) |
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| void | message_port_pub (pmt::pmt_t port_id, pmt::pmt_t msg) |
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| void | message_port_sub (pmt::pmt_t port_id, pmt::pmt_t target) |
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| void | message_port_unsub (pmt::pmt_t port_id, pmt::pmt_t target) |
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| virtual bool | message_port_is_hier (pmt::pmt_t port_id) |
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| virtual bool | message_port_is_hier_in (pmt::pmt_t port_id) |
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| virtual bool | message_port_is_hier_out (pmt::pmt_t port_id) |
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| pmt::pmt_t | message_ports_in () |
| | Get input message port names. More...
|
| |
| pmt::pmt_t | message_ports_out () |
| | Get output message port names. More...
|
| |
| void | _post (pmt::pmt_t which_port, pmt::pmt_t msg) |
| |
| bool | empty_p (pmt::pmt_t which_port) |
| | is the queue empty? More...
|
| |
| bool | empty_p () |
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| bool | empty_handled_p (pmt::pmt_t which_port) |
| | are all msg ports with handlers empty? More...
|
| |
| bool | empty_handled_p () |
| |
| size_t | nmsgs (pmt::pmt_t which_port) |
| | How many messages in the queue? More...
|
| |
| void | insert_tail (pmt::pmt_t which_port, pmt::pmt_t msg) |
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| pmt::pmt_t | delete_head_nowait (pmt::pmt_t which_port) |
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| pmt::pmt_t | delete_head_blocking (pmt::pmt_t which_port) |
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| msg_queue_t::iterator | get_iterator (pmt::pmt_t which_port) |
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| void | erase_msg (pmt::pmt_t which_port, msg_queue_t::iterator it) |
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| virtual bool | has_msg_port (pmt::pmt_t which_port) |
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| virtual void | setup_rpc () |
| | Set up the RPC registered variables. More...
|
| |
| bool | is_rpc_set () |
| | Ask if this block has been registered to the RPC. More...
|
| |
| void | rpc_set () |
| | When the block is registered with the RPC, set this. More...
|
| |
| virtual bool | check_topology (int ninputs, int noutputs) |
| | Confirm that ninputs and noutputs is an acceptable combination. More...
|
| |
| template<typename T > |
| void | set_msg_handler (pmt::pmt_t which_port, T msg_handler) |
| | Set the callback that is fired when messages are available. More...
|
| |
| | msg_accepter () |
| |
| | ~msg_accepter () |
| |
| void | post (pmt::pmt_t which_port, pmt::pmt_t msg) |
| | send msg to msg_accepter on port which_port More...
|
| |
| | msg_accepter () |
| |
Timing synchronizer using polyphase filterbanks.
This block performs timing synchronization for PAM signals by minimizing the derivative of the filtered signal, which in turn maximizes the SNR and minimizes ISI.
This approach works by setting up two filterbanks; one filterbank contains the signal's pulse shaping matched filter (such as a root raised cosine filter), where each branch of the filterbank contains a different phase of the filter. The second filterbank contains the derivatives of the filters in the first filterbank. Thinking of this in the time domain, the first filterbank contains filters that have a sinc shape to them. We want to align the output signal to be sampled at exactly the peak of the sinc shape. The derivative of the sinc contains a zero at the maximum point of the sinc (sinc(0) = 1, sinc(0)' = 0). Furthermore, the region around the zero point is relatively linear. We make use of this fact to generate the error signal.
If the signal out of the derivative filters is d_i[n] for the ith filter, and the output of the matched filter is x_i[n], we calculate the error as: e[n] = (Re{x_i[n]} * Re{d_i[n]} + Im{x_i[n]} * Im{d_i[n]}) / 2.0 This equation averages the error in the real and imaginary parts. There are two reasons we multiply by the signal itself. First, if the symbol could be positive or negative going, but we want the error term to always tell us to go in the same direction depending on which side of the zero point we are on. The sign of x_i[n] adjusts the error term to do this. Second, the magnitude of x_i[n] scales the error term depending on the symbol's amplitude, so larger signals give us a stronger error term because we have more confidence in that symbol's value. Using the magnitude of x_i[n] instead of just the sign is especially good for signals with low SNR.
The error signal, e[n], gives us a value proportional to how far away from the zero point we are in the derivative signal. We want to drive this value to zero, so we set up a second order loop. We have two variables for this loop; d_k is the filter number in the filterbank we are on and d_rate is the rate which we travel through the filters in the steady state. That is, due to the natural clock differences between the transmitter and receiver, d_rate represents that difference and would traverse the filter phase paths to keep the receiver locked. Thinking of this as a second-order PLL, the d_rate is the frequency and d_k is the phase. So we update d_rate and d_k using the standard loop equations based on two error signals, d_alpha and d_beta. We have these two values set based on each other for a critically damped system, so in the block constructor, we just ask for "gain," which is d_alpha while d_beta is equal to (gain^2)/4.
The block's parameters are:
sps: The clock sync block needs to know the number of samples per symbol, because it defaults to return a single point representing the symbol. The sps can be any positive real number and does not need to be an integer.
taps: One of the most important parameters for this block is the taps of the filter. One of the benefits of this algorithm is that you can put the matched filter in here as the taps, so you get both the matched filter and sample timing correction in one go. So create your normal matched filter. For a typical digital modulation, this is a root raised cosine filter. The number of taps of this filter is based on how long you expect the channel to be; that is, how many symbols do you want to combine to get the current symbols energy back (there's probably a better way of stating that). It's usually 5 to 10 or so. That gives you your filter, but now we need to think about it as a filter with different phase profiles in each filter. So take this number of taps and multiply it by the number of filters. This is the number you would use to create your prototype filter. When you use this in the PFB filerbank, it segments these taps into the filterbanks in such a way that each bank now represents the filter at different phases, equally spaced at 2pi/N, where N is the number of filters.
filter_size (default=32): The number of filters can also be set and defaults to 32. With 32 filters, you get a good enough resolution in the phase to produce very small, almost unnoticeable, ISI. Going to 64 filters can reduce this more, but after that there is very little gained for the extra complexity.
init_phase (default=0): The initial phase is another settable parameter and refers to the filter path the algorithm initially looks at (i.e., d_k starts at init_phase). This value defaults to zero, but it might be useful to start at a different phase offset, such as the mid-point of the filters.
max_rate_deviation (default=1.5): The next parameter is the max_rate_devitation, which defaults to 1.5. This is how far we allow d_rate to swing, positive or negative, from 0. Constraining the rate can help keep the algorithm from walking too far away to lock during times when there is no signal.
osps (default=1): The osps is the number of output samples per symbol. By default, the algorithm produces 1 sample per symbol, sampled at the exact sample value. This osps value was added to better work with equalizers, which do a better job of modeling the channel if they have 2 samps/sym.
Reference: f. j. harris and M. Rice, "Multirate Digital Filters for Symbol
Timing Synchronization in Software Defined Radios", IEEE Selected Areas in Communications, Vol. 19, No. 12, Dec., 2001.
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.127.1757
Public Types inherited from gr::block