diff --git a/applications/VK_Client.c b/applications/VK_Client.c
index a3e83cd..d20deda 100644
--- a/applications/VK_Client.c
+++ b/applications/VK_Client.c
@@ -35,9 +35,63 @@ static uint8_t socket_tx_buffer[LTE_SOCKET_TX_CHUNK_SIZE];
 static uint8_t socket_rx_buffer[LTE_SOCKET_RX_CHUNK_SIZE];
 static rt_size_t socket_tx_pending = 0;
 static rt_tick_t last_ack_query_tick = 0;
+static rt_tick_t socket_tx_retry_tick = 0;
+static rt_uint8_t socket_tx_retry_count = 0;
+
+typedef struct {
+  rt_tick_t tick;
+  rt_uint32_t fmu_rx_bytes;
+  rt_uint32_t socket_tx_bytes;
+  rt_uint32_t send_ok;
+  rt_uint32_t send_fail;
+  rt_uint32_t acked_bytes;
+  rt_uint32_t queue_drops;
+  rt_uint32_t prompt_timeouts;
+} tx_stat_baseline_t;
+
+static tx_stat_baseline_t tx_stat_baseline;
 
 static void lte_diag_finish_disconnect(void);
 
+static void tx_stat_reset(void) {
+  tx_stat_baseline.tick = rt_tick_get();
+  tx_stat_baseline.fmu_rx_bytes = lte_diag.fmu_rx_bytes;
+  tx_stat_baseline.socket_tx_bytes = lte_diag.socket_tx_bytes;
+  tx_stat_baseline.send_ok = lte_diag.socket_send_ok;
+  tx_stat_baseline.send_fail = lte_diag.socket_send_fail;
+  tx_stat_baseline.acked_bytes = lte_diag.socket_acked_bytes;
+  tx_stat_baseline.queue_drops = lte_diag.tx_queue_drops;
+  tx_stat_baseline.prompt_timeouts = lte_diag.socket_prompt_timeouts;
+}
+
+static rt_uint32_t tx_stat_rate(rt_uint32_t delta, rt_tick_t elapsed) {
+  return elapsed == 0 ? 0 : delta * RT_TICK_PER_SECOND / elapsed;
+}
+
+static void tx_stat_log(void) {
+  rt_tick_t now = rt_tick_get();
+  rt_tick_t elapsed = now - tx_stat_baseline.tick;
+  rt_uint32_t fmu_delta;
+  rt_uint32_t socket_delta;
+
+  if (elapsed < RT_TICK_PER_SECOND * 5) return;
+
+  fmu_delta = lte_diag.fmu_rx_bytes - tx_stat_baseline.fmu_rx_bytes;
+  socket_delta = lte_diag.socket_tx_bytes - tx_stat_baseline.socket_tx_bytes;
+  LOG_I("[TXSTAT] in=%uB/s out=%uB/s q=%u/%u pending=%u drops=%u",
+        tx_stat_rate(fmu_delta, elapsed), tx_stat_rate(socket_delta, elapsed),
+        fmu_net_queue_data_len(), fmu_net_queue_capacity(), socket_tx_pending,
+        lte_diag.tx_queue_drops - tx_stat_baseline.queue_drops);
+  LOG_I("[TXSTAT] ok=%u fail=%u retry=%u ack_delta=%u unacked=%u prompt_to=%u",
+        lte_diag.socket_send_ok - tx_stat_baseline.send_ok,
+        lte_diag.socket_send_fail - tx_stat_baseline.send_fail,
+        socket_tx_retry_count,
+        lte_diag.socket_acked_bytes - tx_stat_baseline.acked_bytes,
+        lte_diag.socket_unacked_bytes,
+        lte_diag.socket_prompt_timeouts - tx_stat_baseline.prompt_timeouts);
+  tx_stat_reset();
+}
+
 no_carrier_match_t _no_carrier_t = {0};
 
 /*关闭TCP连接*/
@@ -53,6 +107,8 @@ void client_tcp_close(Cclient_t *client) {
   BSP_LTE_ClearSocketEvents();
   fmu_net_queue_reset();
   socket_tx_pending = 0;
+  socket_tx_retry_tick = 0;
+  socket_tx_retry_count = 0;
   rt_snprintf(close_cmd, sizeof(close_cmd), AT_QICLOSE, client->connect_ID);
   BSP_LTE_SendCmd(close_cmd, DEFAULT_EXPECT, DEFAULT_ERROR,
                   LTE_CMD_WAIT_QICLOSE);
@@ -412,8 +468,11 @@ int16_t client_tcp_connect(Cclient_t *client) {
   BSP_LTE_ClearSocketEvents();
   fmu_net_queue_reset();
   socket_tx_pending = 0;
+  socket_tx_retry_tick = 0;
+  socket_tx_retry_count = 0;
   BSP_LTE_SetDataTxPaused(false);
   lte_diag_connect_success();
+  tx_stat_reset();
   last_ack_query_tick = lte_diag.connect_tick;
   client->error_cnt = 0;
   lte_dev.reset_flag = DTU_CF_NO_NEED_RESET;
@@ -593,28 +652,44 @@ void client_yield(CLte_dev_t *pLte_dev) {
         socket_tx_pending = fmu_net_queue_get(socket_tx_buffer,
                                               sizeof(socket_tx_buffer));
       }
-      if (socket_tx_pending > 0) {
+      if (socket_tx_pending > 0 &&
+          (socket_tx_retry_tick == 0 ||
+           (rt_int32_t)(rt_tick_get() - socket_tx_retry_tick) >= 0)) {
         socket_result = BSP_LTE_SendSocketData(
             pLte_dev->client1->connect_ID, socket_tx_buffer,
             (uint16_t)socket_tx_pending);
         if (socket_result == 0) {
           socket_tx_pending = 0;
+          socket_tx_retry_tick = 0;
+          socket_tx_retry_count = 0;
         } else if (socket_result < 0) {
           lte_diag_disconnect(LTE_DISC_SOCKET_SEND);
           client_tcp_close(pLte_dev->client1);
           continue;
         } else {
-          rt_thread_mdelay(50);
+          rt_uint32_t retry_delay_ms;
+
+          if (socket_tx_retry_count < 255) socket_tx_retry_count++;
+          retry_delay_ms = socket_tx_retry_count <= 2 ? 100 :
+                           socket_tx_retry_count <= 5 ? 250 : 500;
+          socket_tx_retry_tick =
+              rt_tick_get() + rt_tick_from_millisecond(retry_delay_ms);
+          LOG_W("[TX] retry=%u delay_ms=%u pending=%u", socket_tx_retry_count,
+                retry_delay_ms, socket_tx_pending);
         }
       }
 
-      if (rt_tick_get() - last_ack_query_tick >= RT_TICK_PER_SECOND * 5) {
+      if (!pLte_dev->socket_recv_pending &&
+          rt_tick_get() - last_ack_query_tick >= RT_TICK_PER_SECOND * 5) {
         last_ack_query_tick = rt_tick_get();
         BSP_LTE_QuerySocketSendStatus(pLte_dev->client1->connect_ID);
       }
 
+      tx_stat_log();
+
 #if LTE_SERVER_SILENCE_TIMEOUT_SEC > 0
-      if (rt_tick_get() - last_rx_tick >
+      if (!pLte_dev->socket_recv_pending &&
+          rt_tick_get() - last_rx_tick >
           RT_TICK_PER_SECOND * LTE_SERVER_SILENCE_TIMEOUT_SEC) {
         lte_diag.server_silence_timeout_count++;
         LOG_W("server silence timeout, reconnect\n");
diff --git a/applications/VK_Com.c b/applications/VK_Com.c
index 89aa493..cfca3fe 100644
--- a/applications/VK_Com.c
+++ b/applications/VK_Com.c
@@ -5,6 +5,10 @@
 #include "rtthread.h"
 #include <ipc/ringbuffer.h>
 
+#define DBG_TAG "LINK_LOG"
+#define DBG_LVL DBG_INFO
+#include "rtdbg.h"
+
 #define ENABLE_MEMORY_USAGE_LOG 0
 
 #if ENABLE_MEMORY_USAGE_LOG
@@ -16,11 +20,14 @@
 rt_device_t fmu_com = RT_NULL;
 rt_sem_t fmu_com_rx_sem = RT_NULL;
 
-#define FMU_NET_QUEUE_SIZE 512
+#define FMU_NET_QUEUE_SIZE 768
 static struct rt_ringbuffer fmu_net_queue;
 static struct rt_mutex fmu_net_queue_lock;
 static uint8_t fmu_net_queue_pool[FMU_NET_QUEUE_SIZE];
 static bool fmu_net_queue_ready = false;
+static rt_tick_t tx_queue_drop_log_tick = 0;
+static rt_uint32_t tx_queue_drop_log_bytes = 0;
+static rt_uint32_t tx_queue_drop_log_events = 0;
 
 #if ENABLE_MEMORY_USAGE_LOG
 static rt_size_t thread_stack_used(rt_thread_t thread) {
@@ -96,7 +103,24 @@ rt_size_t fmu_net_queue_put(const uint8_t *data, rt_size_t length) {
   used = rt_ringbuffer_data_len(&fmu_net_queue);
   rt_mutex_release(&fmu_net_queue_lock);
 
-  if (queued < length) lte_diag.tx_queue_drops += length - queued;
+  if (queued < length) {
+    rt_size_t dropped = length - queued;
+    rt_tick_t now = rt_tick_get();
+
+    lte_diag.tx_queue_drops += dropped;
+    tx_queue_drop_log_bytes += dropped;
+    tx_queue_drop_log_events++;
+    if (tx_queue_drop_log_tick == 0) tx_queue_drop_log_tick = now;
+    if (now - tx_queue_drop_log_tick >= RT_TICK_PER_SECOND) {
+      LOG_W("[TXQ] drops=%u events=%u used=%u/%u window_ms=%u",
+            tx_queue_drop_log_bytes, tx_queue_drop_log_events, used,
+            (rt_size_t)FMU_NET_QUEUE_SIZE,
+            now - tx_queue_drop_log_tick);
+      tx_queue_drop_log_tick = now;
+      tx_queue_drop_log_bytes = 0;
+      tx_queue_drop_log_events = 0;
+    }
+  }
   if (used > lte_diag.tx_queue_high_water) lte_diag.tx_queue_high_water = used;
   return queued;
 }
@@ -111,6 +135,18 @@ rt_size_t fmu_net_queue_get(uint8_t *data, rt_size_t length) {
   return read;
 }
 
+rt_size_t fmu_net_queue_data_len(void) {
+  rt_size_t used;
+
+  if (!fmu_net_queue_ready) return 0;
+  rt_mutex_take(&fmu_net_queue_lock, RT_WAITING_FOREVER);
+  used = rt_ringbuffer_data_len(&fmu_net_queue);
+  rt_mutex_release(&fmu_net_queue_lock);
+  return used;
+}
+
+rt_size_t fmu_net_queue_capacity(void) { return FMU_NET_QUEUE_SIZE; }
+
 void fmu_net_queue_reset(void) {
   if (!fmu_net_queue_ready) return;
   rt_mutex_take(&fmu_net_queue_lock, RT_WAITING_FOREVER);
diff --git a/applications/VK_Com.h b/applications/VK_Com.h
index edd12eb..83c8685 100644
--- a/applications/VK_Com.h
+++ b/applications/VK_Com.h
@@ -17,6 +17,8 @@ rt_device_t fmu_com_get(void);
 int fmu_com_register(rt_device_t com_dev);
 rt_size_t fmu_net_queue_put(const uint8_t *data, rt_size_t length);
 rt_size_t fmu_net_queue_get(uint8_t *data, rt_size_t length);
+rt_size_t fmu_net_queue_data_len(void);
+rt_size_t fmu_net_queue_capacity(void);
 void fmu_net_queue_reset(void);
 
 #ifdef __cplusplus
diff --git a/lib/mavlink b/lib/mavlink
index 10ab2c9..901131d 160000
--- a/lib/mavlink
+++ b/lib/mavlink
@@ -1 +1 @@
-Subproject commit 10ab2c9cf0b57b58a136412beeea2b0d459073a6
+Subproject commit 901131d3504631175255966012664c450500f259