diff --git a/impl/src/config.h b/impl/src/config.h
index 4e29ffd..37d3c1a 100644
--- a/impl/src/config.h
+++ b/impl/src/config.h
@@ -3,12 +3,14 @@
 
 #include <liquid/liquid.h>
 
-#define CHANNEL_CODE   LIQUID_FEC_CONV_V27P34
-#define MODULATION     LIQUID_MODEM_QAM16
+#define PAYLOAD_CHANNEL_CODE   LIQUID_FEC_CONV_V27P34
+#define PAYLOAD_MODULATION     LIQUID_MODEM_QAM16
 
 #define HEADER_CHANNEL_CODE   LIQUID_FEC_NONE
 #define HEADER_MODULATION     LIQUID_MODEM_QPSK
 
+#define PAYLOAD_CRC_SCHEME    LIQUID_CRC_16
+
 #define PREAMBLE_MSEQ_M       6
 #define PREAMBLE_MSEQ_POLY    LIQUID_MSEQUENCE_GENPOLY_M6
 #define PREAMBLE_MSEQ_INIT    0x00000001
diff --git a/impl/src/main.c b/impl/src/main.c
index 0a8f110..1f26eb1 100644
--- a/impl/src/main.c
+++ b/impl/src/main.c
@@ -30,6 +30,16 @@ void print_complex_array(const char *varname, float complex const *array, size_t
 }
 
 
+void update_nco_pll(nco_crcf nco, float phase_error)
+{
+	static const float pll_alpha = 0.05f;                          // phase adjustment factor
+	static const float pll_beta  = (pll_alpha * pll_alpha) / 2.0f; // frequency adjustment factor
+
+	nco_crcf_adjust_phase(nco, pll_alpha * phase_error);
+	nco_crcf_adjust_frequency(nco, pll_beta * phase_error);
+}
+
+
 int main(void)
 {
 	uint8_t msg_org[] = "Hello Liquid! This is the message to transmit. Hopefully it can be decoded correctly...";
@@ -37,14 +47,14 @@ int main(void)
 	uint8_t header[4];
 
 	fec hdr_fec = fec_create(HEADER_CHANNEL_CODE, NULL);
-	fec payload_fec = fec_create(CHANNEL_CODE, NULL);
+	fec payload_fec = fec_create(PAYLOAD_CHANNEL_CODE, NULL);
 
 	modem hdr_demod = modem_create(HEADER_MODULATION);
-	modem payload_demod = modem_create(MODULATION);
+	modem payload_demod = modem_create(PAYLOAD_MODULATION);
 
 	channel_cccf channel = channel_cccf_create();
 
-	float snr = 12.0f;
+	float snr = 7.0f;
 	channel_cccf_add_awgn(channel, -snr, snr);
 	channel_cccf_add_carrier_offset(channel, 0.20f, 1.00f);
 
@@ -210,7 +220,11 @@ int main(void)
 					if(symbol_counter < hdr_len_symbols) {
 						unsigned int sym_demod;
 						modem_demodulate(hdr_demod, mixed_sample, &sym_demod);
-						printf("Sym: %d; Phase error: %f\n", sym_demod, modem_get_demodulator_phase_error(hdr_demod));
+
+						float phase_error = modem_get_demodulator_phase_error(hdr_demod);
+						printf("Sym: %d; Phase error: %f\n", sym_demod, phase_error);
+
+						update_nco_pll(carrier_fine_nco, phase_error);
 
 						symbols_cpx[symbol_counter] = mixed_sample;
 						symbols_int[symbol_counter] = sym_demod;
@@ -230,7 +244,7 @@ int main(void)
 						payload_len_bytes = ((uint16_t)header[0] << 8) | header[1];
 						payload_crc       = ((uint16_t)header[2] << 8) | header[3];
 
-						payload_len_enc_bytes = fec_get_enc_msg_length(CHANNEL_CODE, payload_len_bytes);
+						payload_len_enc_bytes = fec_get_enc_msg_length(PAYLOAD_CHANNEL_CODE, payload_len_bytes);
 						payload_len_symbols = (payload_len_enc_bytes * 8 + payload_bps - 1) / payload_bps;
 
 						printf("=== DECODED HEADER ===\n");
@@ -250,7 +264,11 @@ int main(void)
 					if(symbol_counter < payload_len_symbols) {
 						unsigned int sym_demod;
 						modem_demodulate(payload_demod, mixed_sample, &sym_demod);
-						printf("Sym: %d; Phase error: %f\n", sym_demod, modem_get_demodulator_phase_error(payload_demod));
+
+						float phase_error = modem_get_demodulator_phase_error(payload_demod);
+						printf("Sym: %d; Phase error: %f\n", sym_demod, phase_error);
+
+						update_nco_pll(carrier_fine_nco, phase_error);
 
 						symbols_cpx[symbol_counter] = mixed_sample;
 						symbols_int[symbol_counter] = sym_demod;
@@ -268,11 +286,13 @@ int main(void)
 
 						fec_decode(payload_fec, payload_len_bytes, payload_enc, payload);
 
+						int valid = crc_validate_message(PAYLOAD_CRC_SCHEME, payload, payload_len_bytes, payload_crc);
+
 						payload[payload_len_bytes] = '\0';
 
-						printf("=== DECODED PAYLOAD ===\n");
+						printf("=== DECODED PAYLOAD (valid: %d) ===\n", valid);
 						printf("%s\n", payload);
-						printf("=======================\n");
+						printf("==================================\n");
 
 						dump_array_cf(symbols_cpx, symbol_counter, 1.0f, "/tmp/payload.cpx");
 						rx_state = RX_STATE_ACQUISITION;
diff --git a/impl/src/packet_mod.c b/impl/src/packet_mod.c
index 3cf28ad..aa11368 100644
--- a/impl/src/packet_mod.c
+++ b/impl/src/packet_mod.c
@@ -1,3 +1,4 @@
+#include <liquid/liquid.h>
 #include <string.h>
 
 #include "preamble.h"
@@ -12,8 +13,8 @@ result_t packet_mod_init(packet_mod_ctx_t *ctx)
 
 	ctx->length = 0;
 
-	ctx->fec   = fec_create(CHANNEL_CODE, NULL);
-	ctx->modem = modem_create(MODULATION);
+	ctx->fec   = fec_create(PAYLOAD_CHANNEL_CODE, NULL);
+	ctx->modem = modem_create(PAYLOAD_MODULATION);
 
 	ctx->hdr_fec   = fec_create(HEADER_CHANNEL_CODE, NULL);
 	ctx->hdr_modem = modem_create(HEADER_MODULATION);
@@ -72,6 +73,7 @@ result_t packet_mod_set_data(packet_mod_ctx_t *ctx, const unsigned char *data, s
 	memcpy(ctx->pkt_bytes, data, length);
 	ctx->length = length;
 
+	ctx->raw_data_crc = crc_generate_key(PAYLOAD_CRC_SCHEME, data, length);
 	ctx->raw_data_len = length;
 
 	ctx->state = DATA_RAW;
@@ -86,7 +88,7 @@ result_t packet_mod_encode(packet_mod_ctx_t *ctx)
 		return ERR_INVALID_STATE;
 	}
 
-	unsigned int enc_length = fec_get_enc_msg_length(CHANNEL_CODE, ctx->length);
+	unsigned int enc_length = fec_get_enc_msg_length(PAYLOAD_CHANNEL_CODE, ctx->length);
 
 	unsigned char *enc_msg = malloc(enc_length);
 	if(!enc_msg) {