4G Signal Bars drop from 5 to 2 after 30 minutes and stays that way

[pollardd]

Hi Guys,

I have a LB2120 and it is working fairly well.

I'm in a regional area and have it connected to an external 4G antenna.

It's permanently connected to 4G. It is not used in fail over mode.

When I first boot the device it shows 5 signal bars on the modem and it goes like a rocket.

Ping 39ms 53Mbps Down and 28Mbps Up.  

After around 30 minutes it drops back to 2 signal bars and and stays that way indefinately

The speed is considerably slower especially the upload speed.

Ping 39ms 29Mbps Down and 2.85Mbps Up.

This is very consistant.  It does it every time I reboot.

Does anyone know what is going on here?

By The Way the firmware is up to date according to the user interface but I can't actually see the version number anywhere.

[Blanca_O]

Hi @pollardd

Welcome to NETGEAR Community! 

What is the network type (4G, 3G, 2G) when the signal bars dropped to 2 bars? 

Regards, 
Blanca 
Community Team
 

[pollardd]

Hi Blanca,

The connection is always 4G when I have 5 Bars and when I have 2 Bars.

Thanks

David

[Blanca_O]

Hi David, 

You mentioned that LB2120 is connected to an external 4G antenna. Have you tried another external antenna? 

Regards, 
Blanca 
Community Team

[pollardd]

Hi Blanca,
That's a good idea unfortunately I only have one antenna.
When I say it is external it's bolted to the outside of my house on a mast.
It's a good quality directional antenna worth a couple of hundred dollars so I'd be very surprised if the antenna could cause this problem. It used to work consistently on my previous modem.
I actually have a second LB2120 for use at a different site and I thought I’d try that one before I deploy it. The second device starts on 5 bars for about 30 seconds then drops back to 2.
I have done some more speed tests on both devices, while on 2 signal bars and the speed is OK. Consistantly it obtains a Ping 31ms Download ~45Mbps Upload ~ 10Mbps.
I think we will have to leave this as an "anomaly".  I was hoping there was some power saving setting I could change to keep it at 5 bars but it seems I'm dreaming 🙂

Thanks for your assistance.

David

[psynpase]

HI,

Only recently joined the community with a move from Huawei to a Netgear LB2120. 

I also recently installed a MIMO pair of external antenna.  With the Huawei I found that I had the same problem as you ( but typically after only 5 minutes).  The Huawei has a slightly more sensitive rf front end than the Netgear, but in this case it did me no favours.  The service provider would note that I had good signal strength and switch me to the high band, with major consequences :- my download/upload rate dropped from 80/20 Meg to 30/0.4 Meg.

The move to a Netgear LB2120 gives me 2dB less, just enough to avoid the telco shifting band! (And also provides me with Band 28 fallback) 

Of course this may not be your problem, but check to see what your telcos policy is  And check the modem status; you will see the band you are currently on near the bottom of the screen

[pollardd]

 Hi Psynapse,

My modem is still behaving much the same as when I originally posted.

  I can't see the band that it is currently connected with.  I have my device in bridge mode as I have a Cisco router behind it and all the routing happens there.  The LB2120 screens are actually really bland in bridge mode.  I have an icon with 2/5 signal bars and it usually says 3G these days.  I'd hold out no hope of ringing Telstra and asking them about this stuff and actually getting any reasonable response.  Just for fun I did another speed test and Ping is 50ms Download is 6.0Mbps Upload is 1.24.  This meets my needs so I just put up with it.

[psynpase]

Hi,

Well I have been doing a little more investigation.  On Github I found that somebody had written some python (called eternalegypt) .... for which many thanks.  This allows you to interrogate the modem without having to go to the web page.  By modifying one of these scripts and running it under cron (every 5 minutes) I have been able to log statistics.  These show quite clearly that the modem starts by connecting to the B3 band and after a certain (and variable) period of time switches to the higher frequency B7 band.  In the process I lose 10dB of signal strength and a great deal of upload performance (a factor of 10-20, ie from 20Mbps to less that 1).  I am pretty sure that this is frequency management by the cell tower and nothing to do with the modem. However I would love to be able to lock the modem down to bands below 2GHz because I live in a rural area and radio propogation is not obvious.

My partial work around is to reboot the modem before I need to use it (simply going offline and then online does NOT resolve the problem),  But in your case and IF you have the same problem then the speed with which this all happens gives you very little time to work.

For reference the B7 signal comes in at RSSI  -90dB whilst the B3 signal is in the -77 to -81 range. The RSRP levels are more marked -120dB vs-105dB.   If this is a firmware issue,  I certainly hope that Netgear fix it!

[psynpase]

Just an afterthought, perhaps your aerial is too good .... what RSSI do you get when you first reboot the modem? and what does it drop to later?

The attached my measurements over 24 hours , the yellow trace is RSSI, the blue RSRP

[pollardd]

Hey @psynpase ,
I'm just wondering if you have reached any conclusions with your diagnosis?

My modem started doing more weird stuff today.  This morning it was not connected to Telstra and it stayed off for about 5 hours.  No amount of rebooting could get it back on line.  I had to fall back to my satalite connection with its painfully slow round trip times.

Suddnely with out me doing anything I looked over to my modem and it had 5 Bars.  I ran speedtest.net and I was getting around 50Mbps up and down!  After 20 minutes or so it has dropped back down to 1 or 2 bars again and 30 down 5 up aka normal.

I was wondering if I could get a copy of the python script you have been using to log data.  I found the author on github but I don't really need to reinvent the wheel if you have made some useful changes to the script.

Thanks

David.

[psynpase]

Hi Pollard,

First things first!  I am going to be looking at my data for a good twelve months yet,  because where I am the signal path passes through vegetation and I am expecting a degradation in signal quality as spring arrives in the northern hemisphere. So this will be the first of several updates.

I have been logging data for around a month now and apart from occasional storms I expect the signal path has been pretty stable .... which is more that I can say for the signal!  My own experience (reinforced by what I have read elsewhere) is that the service providers play fast and loose with band allocations and in a dynamic manner (Just as a point of reference, here in France I use "Free" largely because it uses its own microwave trunk infrastructure, which is currently less burdened that the infrastructure of the ex state owned France Telecom, which nearly everybody uses). 

It is still early days, but there is a strong trend for the ISP to switch me to the highest frequency band available, B7.  Despite having a mast mounted MIMO array, the signal staggers in at around -118db, with OKish download speeds but almost not existant <0.4Mbps upload speeds.  A modem reset gets me back to band B3 which (depending on other users present on the net) will get me anything up to 90/20Mbps ,  very nice thank you.  After a variable time (which seems to be related to network load) I will drop back down to B7.  An interesting thing to note is that this will happen regardless of whether the modem is left in the "connected" or "disconnected" state. Which poses the question as to what "connected" actually means to Netgear.

On just one occasion the modem has switched to B28 (which, btw, the Netgear reports as "unknown" band, but with a correct channel number).

On very few occasions have I seen the network "upgrade" me from B7 to B3.

As a point of pure conjecture, I believe that Free brought their B7 band allocation first, rolled out their 4G infrastructure in a hurry, even to rural areas where 2.5GHz propogation is problematic. They then acquired a B3 licence and recently a B28.  Users with handsets or tablets hence struggle to get B7, nearly everybody tries to get onto B3, because at the moment B28 is too new for most in the field hardware.

Second point.  Python scripts.  I use Linux, so I cannot give chapter and verse for windows, but hey it is python, so how hard can it be? But then I regard myself as just a script kiddy:- all credit to the original author.

I have modded one file (the main one) in the original distro, in order for it to report more parameters. And added two example scipts, one to report stats in a readable form, the other to generate time stamped csv values for import to a speadsheet.

So eg I can run the logging script manually with

/usr/bin/env python3 /home/myusername/Downloads/eternalegypt-master/examples/logstats.py <netgear ip> <netgear password>

I have added this line to my (user) cron file.

And, in the right directory the stats reporter is run simply by

./status2.py <netgear ip> <netgear password>

The additions/modifications I have made to the original distro are in the attached zip .... note that you will have to edit logstats.py to reflect the path to your logfile, because I did not make this a parameter specified at run time.

Postscript, no zips to tne community board 😞

Good luck

[psynpase]

Modified eternalegypt.py

"""Library for interfacing with Netgear LTE modems."""
import logging
import re
import json
from functools import wraps
from datetime import datetime
import asyncio
from aiohttp.client_exceptions import ClientError
import async_timeout
import attr
import flatten_json

TIMEOUT = 3

_LOGGER = logging.getLogger(__name__)

class Error(Exception):
"""Base class for all exceptions."""

@attr.s
class SMS:
"""An SMS message."""
id = attr.ib()
timestamp = attr.ib()
unread = attr.ib()
sender = attr.ib()
message = attr.ib()

@attr.s
class Information:
"""Various information from the modem."""
serial_number = attr.ib(default=None)
usage = attr.ib(default=None)
upstream = attr.ib(default=None)
wire_connected = attr.ib(default=None)
mobile_connected = attr.ib(default=None)
connection_text = attr.ib(default=None)
connection_type = attr.ib(default=None)
current_nw_service_type = attr.ib(default=None)
current_ps_service_type = attr.ib(default=None)
register_network_display = attr.ib(default=None)
roaming = attr.ib(default=None)
radio_quality = attr.ib(default=None)
rx_level = attr.ib(default=None)
tx_level = attr.ib(default=None)
current_band = attr.ib(default=None)
cell_id = attr.ib(default=None)
sms = attr.ib(factory=list)
items = attr.ib(factory=dict)

def autologin(function, timeout=TIMEOUT):
"""Decorator that will try to login and redo an action before failing."""
@wraps(function)
async def wrapper(self, *args, **kwargs):
"""Wrap a function with timeout."""
try:
async with async_timeout.timeout(timeout):
return await function(self, *args, **kwargs)
except (asyncio.TimeoutError, ClientError, Error):
pass

_LOGGER.debug("autologin")
try:
async with async_timeout.timeout(timeout):
await self.login()
return await function(self, *args, **kwargs)
except (asyncio.TimeoutError, ClientError, Error):
raise Error(str(function))

return wrapper

@attr.s
class LB2120:
"""Class for Netgear LB2120 interface."""

hostname = attr.ib()
websession = attr.ib()

password = attr.ib(default=None)
token = attr.ib(default=None)

listeners = attr.ib(init=False, factory=list)
max_sms_id = attr.ib(init=False, default=None)

@property
def _baseurl(self):
return "http://{}/".format(self.hostname)

def _url(self, path):
"""Build a complete URL for the device."""
return self._baseurl + path

async def add_sms_listener(self, listener):
"""Add a listener for new SMS."""
self.listeners.append(listener)

async def logout(self):
"""Cleanup resources."""
self.websession = None
self.token = None

async def login(self, password=None):
"""Create a session with the modem."""
# Work around missing https://github.com/aio-libs/aiohttp/pull/3576
try:
await self._login(password)
except (asyncio.TimeoutError, ClientError, Error):
await self._login(password)

async def _login(self, password=None):
"""Create a session with the modem."""
if password is None:
password = self.password
else:
self.password = password

try:
async with async_timeout.timeout(TIMEOUT):
url = self._url('model.json')
async with self.websession.get(url) as response:
data = json.loads(await response.text())
self.token = data.get('session', {}).get('secToken')

if self.token is None:
_LOGGER.error("No token found during login")
raise Error()

_LOGGER.debug("Token: %s", self.token)

url = self._url('Forms/config')
data = {
'session.password': password,
'token': self.token
}
async with self.websession.post(url, data=data) as response:
_LOGGER.debug("Got cookie with status %d", response.status)

except (asyncio.TimeoutError, ClientError, Error):
raise Error("Could not login")

@autologin
async def sms(self, phone, message):
"""Send a message."""
_LOGGER.debug("Send to %s via %s len=%d",
phone, self._baseurl, len(message))

url = self._url('Forms/smsSendMsg')
data = {
'sms.sendMsg.receiver': phone,
'sms.sendMsg.text': message,
'sms.sendMsg.clientId': __name__,
'action': 'send',
'token': self.token
}
async with self.websession.post(url, data=data) as response:
_LOGGER.debug("Sent message with status %d", response.status)

def _config_call(self, key, value):
"""Set a configuration key to a certain value."""
url = self._url('Forms/config')
data = {
key: value,
'err_redirect': '/error.json',
'ok_redirect': '/success.json',
'token': self.token
}
return self.websession.post(url, data=data)

@autologin
async def disconnect_lte(self):
"""Do an LTE disconnect."""
async with self._config_call('wwan.connect', 'Disconnect') as response:
_LOGGER.debug("Disconnected LTE with status %d", response.status)

@autologin
async def connect_lte(self):
"""Do an LTE reconnect."""
async with self._config_call('wwan.connect', 'DefaultProfile') as response:
_LOGGER.debug("Connected to LTE with status %d", response.status)

@autologin
async def delete_sms(self, sms_id):
"""Delete a message."""
async with self._config_call('sms.deleteId', sms_id) as response:
_LOGGER.debug("Delete %d with status %d", sms_id, response.status)

@autologin
async def set_failover_mode(self, mode):
"""Set failover mode."""
modes = {
'auto': 'Auto',
'wire': 'WAN',
'mobile': 'LTE',
}

if mode not in modes.keys():
_LOGGER.error("Invalid mode %s not %s", mode, "/".join(modes.keys()))
return

async with self._config_call('failover.mode', modes[mode]) as response:
_LOGGER.debug("Set mode to %s", mode)

@autologin
async def set_autoconnect_mode(self, mode):
"""Set autoconnect mode."""
modes = {
'never': 'Never',
'home': 'HomeNetwork',
'always': 'Always',
}

if mode not in modes.keys():
_LOGGER.error("Invalid mode %s not %s", mode, "/".join(modes.keys()))
return

async with self._config_call('wwan.autoconnect', modes[mode]) as response:
_LOGGER.debug("Set mode to %s", mode)

def _build_information(self, data):
"""Read the bits we need from returned data."""
result = Information()

result.serial_number = data['general']['FSN']
result.usage = data['wwan']['dataUsage']['generic']['dataTransferred']
if 'failover' in data
if 'backhaul' in data['failover']:
result.upstream = data['failover']['backhaul']
result.wire_connected = data['failover']['wanConnected']
result.mobile_connected = (data['wwan']['connection'] == 'Connected')
result.connection_text = data['wwan']['connectionText']
result.connection_type = data['wwan']['connectionType']
result.current_nw_service_type = data['wwan']['currentNWserviceType']
result.current_ps_service_type = data['wwan']['currentPSserviceType']
result.register_network_display = data['wwan']['registerNetworkDisplay']
result.roaming = data['wwan']['roaming']
result.radio_quality = data['wwanadv']['radioQuality']
result.rx_level = data['wwanadv']['rxLevel']
result.tx_level = data['wwanadv']['txLevel']
result.current_band = data['wwanadv']['curBand']
result.cell_id = data['wwanadv']['cellId']
result.ecio = data['wwan']['signalStrength']['ecio']
result.rscp = data['wwan']['signalStrength']['rscp']
result.rsrp = data['wwan']['signalStrength']['rsrp']
result.rsrq = data['wwan']['signalStrength']['rsrq']
result.rssi = data['wwan']['signalStrength']['rssi']
result.sinr = data['wwan']['signalStrength']['sinr']
mdy_models = ('MR1100')

for msg in [m for m in data['sms']['msgs'] if 'text' in m]:
# {'id': '6', 'rxTime': '11/03/18 08:18:11 PM', 'text': 'tak tik',
# 'sender': '555-987-654', 'read': False}
try:
if ('model' in data['general'] and data['general']['model'] in mdy_models):
dt = datetime.strptime(msg['rxTime'], '%m/%d/%y %I:%M:%S %p')
else:
dt = datetime.strptime(msg['rxTime'], '%d/%m/%y %I:%M:%S %p')
except ValueError:
dt = None

element = SMS(int(msg['id']), dt, not msg['read'], msg['sender'], msg['text'])
result.sms.append(element)
result.sms.sort(key=lambda sms: sms.id)

result.items = {
key.lower(): value
for key, value in flatten_json.flatten(data, '.').items()
if value != {}
and not re.search(r'\.\d+\.', key)
and not re.search(r'\.end$', key)
and key.lower() not in ('webd.adminpassword', 'session.sectoken', 'wifi.guest.passphrase', 'wifi.passphrase')
}

return result

@autologin
async def information(self):
"""Return the current information."""
url = self._url('model.json')
async with self.websession.get(url) as response:
data = json.loads(await response.text())

try:
result = self._build_information(data)
except KeyError:
_LOGGER.debug("Failed to read information: %s", data)
raise Error()

self._sms_events(result)

return result

def _sms_events(self, information):
"""Send events for each new SMS."""
if not self.listeners:
return

if self.max_sms_id is not None:
new_sms = (s for s in information.sms if s.id > self.max_sms_id)
for sms in new_sms:
for listener in self.listeners:
listener(sms)

if information.sms:
self.max_sms_id = max(s.id for s in information.sms)

class Modem(LB2120):
"""Class for any modem."""

[pollardd]

Hi Psynpase,

Thanks for the very detailed response.  I'm not that deep into all the different bands as you are.  Basically here they are named 3G, 4G, and the new one is named 5G.  I expect the B codes you mentioned are the underlying protocol code names.

I'm a C# programer and haven't played much with Linux for the last 15 years but I'm sure python will come back to me.

I think I'd call my self a script Grand Pa. 🙂

I managed to install Python on windows and when I tried to run the standard eternalegypt.py script it reported a missing dependancy.  I forget the name of that one now 2 days later.  I managed to figure out a bit about the installer and fix them one up but now I have been distracted by actual work. 🙂

I'll let you know when I get it to work or get stuck.  I may even post some of my results here to see if other can make sense of them if I can't.

By The Way.  I thought to get MIMO to work you needed a device with two antenna ports and it being specifically built to take advantage of it.  My LB2120 only has one port.  I found this bit in an online manual.  I'm guessing there is more than one version.

Optional External Antenna

=====================
You can purchase an external multiple input, multiple output (MIMO) antenna for the modem to extend the
mobile broadband signal range indoors or in fringe network areas.
The external antenna plugs into the two antenna connectors on the modem to boost speeds and extend
coverage in buildings or vehicles, or in remote sites where network coverage is sparse.You could, for
example, attach the external antenna on a window with a suction cup

[psynpase]

A couple of months down the line and I thought I would record my "findings"

1)  For me there is no doubt that the telco switches bands based partly on data provided by the modem.  Nothing unusual there.

2) AS I mentioned, my shot at the cell tower passes through seasonal vegetation.  Spring (in the northern hemisphere) is not quite finished yet, but I already have arounf a 3dB drop in signal strength and 3-4 in "quality".  This has halved both up and down datarate (Although the coronavirus may well have changed traffic patterns).  I maybe wrong, but the modem seems to switch between one modulation scheme and another at a quality of 40.  For me this is ammoying because I used to be just above 40 and now am just below 40. But the laws of physics are laws.

3) The only upside to this is that the Telco has stopped trying to switch me to the highest frequency band, simply not enough signal.

4) I brought the LB2120 specifically for its B28 capability.  It has used it just once ( during a heavy downpour).  Data rates are somewhat lower, but a fully acceptable fallback nevertheless.  Note that the firmware correctly identifies Channel number, but comes up with radio band unknown.

FWIW

[pollardd]

That is very interesting information.  As luck would have it I had bought a second one of these modems for the office and they didn't need it so it wound up at my place.  I swapped it out with the original.  The only thing I'm doing differently now is I have it in router mode instead of bridge mode.  In bridge mode my Cisco IPSEC VPN would drop out every few days and I'd have to reboot things a few times until it all got itself sorted out again.  Used to take about 15 minutes.

I have done a few speed tests over the last couple of days and speed I'm getting now is way better than I have had in the past.

50.03Mbps Down and 12.43 Mbps Up.  This is still with only two bars on on the signal strength metre.

I did go and take a look at the data collection tool you mentioned but I never got to the bottom of making it work for me.

The corona virus got in the way when I suddently had to set up 30 staff to work from home.  I think my speed increase may also have somthing to do with the Telco suddenly supplying more band width to the network.  It will be interesting to see if it mysteriously slows back down once the health crisis has passed.

After changing modems the lights are doing the same thing.  5 for a while then dropping back down to 2.

In Router mode with my PC behind another Cisco Router I'm also now doing double NAT and I still good speed.

So this has become an interesting anomaly.  I thought the signal strength would play a bigger part in the achievable speed.

Maybe I'll do more analysis if I get bored one day.