diff --git a/cellular/src/iir_filter.rs b/cellular/src/iir_filter.rs
new file mode 100644
index 0000000..246b1a1
--- /dev/null
+++ b/cellular/src/iir_filter.rs
@@ -0,0 +1,36 @@
+struct IIRFilter {
+    iter: i32,
+    a0: f64,
+    a1: f64,
+    a2: f64,
+    b1: f64,
+    b2: f64,
+    z1: f64,
+    z2: f64,
+}
+
+impl IIRFilter {
+    pub fn lowpass_init(&mut self, frequency: f64, samplerate: i32, iterations: i32) {
+
+    }
+
+    pub fn highpass_init(&mut self, frequency: f64, samplerate: i32, iterations: i32) {
+
+    }
+
+    pub fn bandpass_init(&mut self, frequency: f64, samplerate: i32, iterations: i32) {
+
+    }
+
+    pub fn notch_init(&mut self, frequency: f64, samplerate: i32, iterations: i32, Q: f64) {
+
+    }
+
+    pub fn process(&mut self, samples: Sample, length: i32) {
+
+    }
+
+    pub fn process_baseband(&mut self, filter: IIRFilter, baseband: f64, length: i32) {
+
+    }
+}
\ No newline at end of file
diff --git a/cellular/src/libmobile_sender.rs b/cellular/src/libmobile_sender.rs
new file mode 100644
index 0000000..2ba2b87
--- /dev/null
+++ b/cellular/src/libmobile_sender.rs
@@ -0,0 +1,45 @@
+enum PagingSignal {
+    NONE = 0,
+    TONE,
+    NOTONE,
+    POSITIVE,
+    NEGATIVE,
+}
+
+struct Sender {
+    // System Info
+    channel: char,
+    send_freq: f64,
+    recv_freq: f64,
+    
+    // FM/AM levels
+    am: i32,
+    max_deviation: f64,
+    max_modulation: f64,
+    speech_deviation: f64,
+    modulation_index: f64,
+    max_display: f64,
+
+    // Audio
+    audio: void,
+    device: char,
+    audio_open: void,
+    audio_start: i32,
+    audio_close: void,
+    audio_write: i32,
+    audio_get_tosend: i32,
+    samplerate: i32,
+    samplerate_state: SampleRate,
+    rx_gain: f64,
+    tx_gain: f64,
+    pre_emphasis: i32,
+    de_emphasis: i32,
+    epmphasis_state: EmphasisState,
+
+    // Loopback
+    loopback: i32,
+
+    // Record & Playback
+    
+
+}
\ No newline at end of file
diff --git a/cellular/src/main.rs b/cellular/src/main.rs
index 11ae420..aebd30a 100644
--- a/cellular/src/main.rs
+++ b/cellular/src/main.rs
@@ -3,6 +3,10 @@ use std::io::{stdout, BufWriter};
 
 mod sdr;
 mod amps;
+mod libmobile_sender;
+mod iir_filter;
+mod samplerate;
+
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let stdout = stdout();
     let message = String::from("Welcome to the Cellular Revolution!");
diff --git a/cellular/src/samplerate.rs b/cellular/src/samplerate.rs
new file mode 100644
index 0000000..4d38fae
--- /dev/null
+++ b/cellular/src/samplerate.rs
@@ -0,0 +1,45 @@
+struct SampleRate {
+    factor: f64,
+    filter_cutoff: f64,
+    down: DownSampler,
+    up: UpSampler,
+}
+
+struct DownSampler {
+    lp: IIRFilter,
+    last_sample: Sample,
+    in_index: f64,
+}
+
+struct UpSampler {
+    lp: IIRFilter,
+    current_sample: Sample,
+    last_sample: Sample,
+    in_index: f64,
+}
+
+impl SampleRate {
+    pub fn init(&mut self, low_samplerate: f64, high_samplerate: f64, filter_cutoff: f64) -> Result<(), i32> {
+        // Implementation goes here
+
+        Ok(())
+        // or Err(error_code) if there's an error
+    }
+
+    pub fn downsample(&mut self, state: SampleRate, samples: Sample, input_num: i32) -> Result<(), i32> {
+        Ok(())
+    }
+
+    pub fn upsample_input_num(&mut self, state: SampleRate, output_num: i32) -> Result<(), i32> {
+        Ok(())
+    }
+
+    pub fn upsample_output_num(&mut self, state: SampleRate, input_num: i32) -> Result<(), i32> {
+        Ok(())
+    }
+
+    pub fn upsample(&mut self, state: SampleRate, input: Sample, input_num: i32, output: Sample, output_num: i32) {
+        
+    } 
+
+}
\ No newline at end of file