Wi-Fi is very unstable on Pi 3

Question

Raspberry Pi Spec.

Model: Raspberry Pi 3 Model B V1.2

OS: Raspbian Stretch Lite

Problem

I'm using Wi-Fi pocket (like a router).

My macbook is connected with Wi-Fi pocket well.

My iPhone is connected with Wi-Fi pocket well.

My Raspberry Pi is connected with this same Wi-Fi pocket.

But the connection of Wi-Fi is really unstable with Raspberry-Pi.

For example, if I type iwconfig 100 times into my Raspberry Pi, it shows Access Point : Not-Associated 94 times, and Access Point : 00:1D:93:97:89:68 only 6 times.

This is my Wi-Fi info.

And if I type journalctl -b -e it shows me messages below.

pi@raspberrypi:~ $ journalctl -b -e
Nov 14 03:10:14 raspberrypi dhcpcd[629]: wlan0: carrier acquired
Nov 14 03:10:14 raspberrypi dhcpcd[629]: wlan0: IAID eb:0f:33:b1
Nov 14 03:10:14 raspberrypi dhcpcd[629]: wlan0: adding address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:14 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:14 raspberrypi dhcpcd[629]: wlan0: carrier lost
Nov 14 03:10:14 raspberrypi dhcpcd[629]: wlan0: deleting address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:14 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:26 raspberrypi dhcpcd[629]: wlan0: carrier acquired
Nov 14 03:10:26 raspberrypi dhcpcd[629]: wlan0: IAID eb:0f:33:b1
Nov 14 03:10:26 raspberrypi dhcpcd[629]: wlan0: adding address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:26 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:26 raspberrypi dhcpcd[629]: wlan0: carrier lost
Nov 14 03:10:26 raspberrypi dhcpcd[629]: wlan0: deleting address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:27 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: carrier acquired
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: IAID eb:0f:33:b1
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: adding address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:39 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: carrier lost
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: deleting address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: carrier acquired
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: IAID eb:0f:33:b1
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: adding address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:39 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: carrier lost
Nov 14 03:10:39 raspberrypi dhcpcd[629]: wlan0: deleting address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:40 raspberrypi dhcpcd[629]: wlan0: carrier acquired
Nov 14 03:10:40 raspberrypi dhcpcd[629]: wlan0: IAID eb:0f:33:b1
Nov 14 03:10:40 raspberrypi dhcpcd[629]: wlan0: adding address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:40 raspberrypi dhcpcd[629]: wlan0: carrier lost
Nov 14 03:10:40 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:40 raspberrypi dhcpcd[629]: wlan0: deleting address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:41 raspberrypi dhcpcd[629]: wlan0: carrier acquired
Nov 14 03:10:41 raspberrypi dhcpcd[629]: wlan0: IAID eb:0f:33:b1
Nov 14 03:10:41 raspberrypi dhcpcd[629]: wlan0: adding address fe80::f55e:f571:d55b:9cd6
Nov 14 03:10:41 raspberrypi dhcpcd[629]: wlan0: carrier lost
Nov 14 03:10:41 raspberrypi kernel: brcmfmac: brcmf_link_down: WLC_DISASSOC failed (-11)
Nov 14 03:10:41 raspberrypi dhcpcd[629]: wlan0: deleting address fe80::f55e:f571:d55b:9cd6

And If I type sudo wpa_supplicant -d -B -c/etc/wpa_supplicant/wpa_supplicant.conf -iwlan0, it shows me messages below.

pi@raspberrypi:~ $ sudo wpa_supplicant -d -B -c/etc/wpa_supplicant/wpa_supplicant.conf -iwlan0
wpa_supplicant v2.4
random: Trying to read entropy from /dev/random
Successfully initialized wpa_supplicant
Initializing interface 'wlan0' conf '/etc/wpa_supplicant/wpa_supplicant.conf' driver 'default' ctrl_interface 'N/A' bridge 'N/A'
Configuration file '/etc/wpa_supplicant/wpa_supplicant.conf' -> '/etc/wpa_supplicant/wpa_supplicant.conf'
Reading configuration file '/etc/wpa_supplicant/wpa_supplicant.conf'
ctrl_interface='DIR=/var/run/wpa_supplicant GROUP=netdev'
update_config=1
country='US'
Priority group 0
   id=0 ssid='comecome'
rfkill: initial event: idx=0 type=1 op=0 soft=0 hard=0
rfkill: initial event: idx=1 type=2 op=0 soft=0 hard=0
nl80211: Supported cipher 00-0f-ac:1
nl80211: Supported cipher 00-0f-ac:5
nl80211: Supported cipher 00-0f-ac:2
nl80211: Supported cipher 00-0f-ac:4
nl80211: Using driver-based off-channel TX
nl80211: Supported vendor command: vendor_id=0x1018 subcmd=1
nl80211: Use separate P2P group interface (driver advertised support)
nl80211: Enable multi-channel concurrent (driver advertised support)
nl80211: use P2P_DEVICE support
nl80211: interface wlan0 in phy phy0
nl80211: Set mode ifindex 3 iftype 2 (STATION)
nl80211: Subscribe to mgmt frames with non-AP handle 0x156a8a0
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=040a
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 04 0a
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=040b
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 04 0b
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=040c
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 04 0c
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=040d
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 04 0d
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=090a
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 09 0a
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=090b
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 09 0b
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=090c
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 09 0c
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=090d
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 09 0d
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=0409506f9a09
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=6): 04 09 50 6f 9a 09
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=7f506f9a09
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=5): 7f 50 6f 9a 09
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=0801
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 08 01
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=06
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=1): 06
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=0a07
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 0a 07
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=0a11
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 0a 11
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=1101
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 11 01
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=1102
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 11 02
nl80211: Register frame type=0xd0 (WLAN_FC_STYPE_ACTION) nl_handle=0x156a8a0 match=0505
nl80211: Register frame command failed (type=208): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=2): 05 05
nl80211: Failed to register Action frame processing - ignore for now
netlink: Operstate: ifindex=3 linkmode=1 (userspace-control), operstate=5 (IF_OPER_DORMANT)
nl80211: driver param='(null)'
Add interface wlan0 to a new radio phy0
nl80211: Regulatory information - country=US (DFS-FCC)
nl80211: 2402-2472 @ 40 MHz 30 mBm
nl80211: 5170-5250 @ 80 MHz 23 mBm
nl80211: 5250-5330 @ 80 MHz 23 mBm (DFS)
nl80211: 5490-5730 @ 160 MHz 23 mBm (DFS)
nl80211: 5735-5835 @ 80 MHz 30 mBm
nl80211: 57240-63720 @ 2160 MHz 40 mBm
nl80211: Added 802.11b mode based on 802.11g information
wlan0: Own MAC address: b8:27:eb:0f:33:b1
wpa_driver_nl80211_set_key: ifindex=3 (wlan0) alg=0 addr=(nil) key_idx=0 set_tx=0 seq_len=0 key_len=0
wpa_driver_nl80211_set_key: ifindex=3 (wlan0) alg=0 addr=(nil) key_idx=1 set_tx=0 seq_len=0 key_len=0
wpa_driver_nl80211_set_key: ifindex=3 (wlan0) alg=0 addr=(nil) key_idx=2 set_tx=0 seq_len=0 key_len=0
wpa_driver_nl80211_set_key: ifindex=3 (wlan0) alg=0 addr=(nil) key_idx=3 set_tx=0 seq_len=0 key_len=0
wpa_driver_nl80211_set_key: ifindex=3 (wlan0) alg=0 addr=(nil) key_idx=4 set_tx=0 seq_len=0 key_len=0
wpa_driver_nl80211_set_key: ifindex=3 (wlan0) alg=0 addr=(nil) key_idx=5 set_tx=0 seq_len=0 key_len=0
wlan0: RSN: flushing PMKID list in the driver
nl80211: Flush PMKIDs
TDLS: TDLS operation not supported by driver
TDLS: Driver uses internal link setup
TDLS: Driver does not support TDLS channel switching
wlan0: WPS: UUID based on MAC address: 68981224-70d8-59d3-9a62-37680e59a7fb
ENGINE: Loading dynamic engine
ENGINE: Loading dynamic engine
EAPOL: SUPP_PAE entering state DISCONNECTED
EAPOL: Supplicant port status: Unauthorized
nl80211: Skip set_supp_port(unauthorized) while not associated
EAPOL: KEY_RX entering state NO_KEY_RECEIVE
EAPOL: SUPP_BE entering state INITIALIZE
EAP: EAP entering state DISABLED
Using existing control interface directory.
ctrl_interface_group=108 (from group name 'netdev')
ctrl_iface bind(PF_UNIX) failed: Address already in use
ctrl_iface exists and seems to be in use - cannot override it
Delete '/var/run/wpa_supplicant/wlan0' manually if it is not used anymore
Failed to initialize control interface 'DIR=/var/run/wpa_supplicant GROUP=netdev'.
You may have another wpa_supplicant process already running or the file was
left by an unclean termination of wpa_supplicant in which case you will need
to manually remove this file before starting wpa_supplicant again.

Failed to add interface wlan0
wlan0: Request to deauthenticate - bssid=00:00:00:00:00:00 pending_bssid=00:00:00:00:00:00 reason=3 state=DISCONNECTED
TDLS: Tear down peers
wlan0: State: DISCONNECTED -> DISCONNECTED
nl80211: Set wlan0 operstate 0->0 (DORMANT)
netlink: Operstate: ifindex=3 linkmode=-1 (no change), operstate=5 (IF_OPER_DORMANT)
EAPOL: External notification - portEnabled=0
EAPOL: External notification - portValid=0
wlan0: WPA: Clear old PMK and PTK
wlan0: Cancelling delayed sched scan
wlan0: Cancelling scan request
wlan0: Cancelling authentication timeout
Remove interface wlan0 from radio phy0
Remove radio phy0
nl80211: deinit ifname=wlan0 disabled_11b_rates=0
nl80211: Remove monitor interface: refcount=0
netlink: Operstate: ifindex=3 linkmode=0 (kernel-control), operstate=6 (IF_OPER_UP)
nl80211: Set mode ifindex 3 iftype 2 (STATION)
nl80211: Unsubscribe mgmt frames handle 0x89de2029 (mode change)

What can I do to fix this?