Connectivity is critical for any organization that depends on reliable internet access in order to function. Cellular networks are high-speed, high-capacity voice and data communication networks with enhanced multimedia and seamless roaming capabilities for supporting cellular devices. With the increase in popularity of cellular devices, these networks are used for more than just entertainment and phone calls. They have become the primary means of communication for finance-sensitive business transactions, emergency services, etc. WAN connectivity options, such as cellular networks, now also serve as a reliable backup internet uplink in the event of a primary uplink failure. This article is aimed at providing an introduction to cellular networks, and terms and technologies for cellular connectivity with Meraki.
As cellular technologies continue to evolve, the industry is seeing a shift in how users connect. Since the launch of the Blackberry for enterprises and then the launch of the consumer grade Androids and iPhones, cellular usage for work has skyrocketed. People cannot work without internet, and any serious business will not survive if its not connected.
As you go through this guide, the bolded terms in the paragraphs are the start of a concept. The paragraph and section ideally gives you context to how the term is used and what it means.
Choosing the Best Carrier
The cellular carrier that best fits your needs depends on your situation. An ideal carrier in San Diego, California will be different than a more rural location like Saskatoon, Canada.
Since cellular technologies are wireless and rely on radios (similar to WiFi), signal and quality is going to make or break that cellular connection. Carriers attempt to blanket the area with a wide variety of coverage with cell base stations (towers). The coverage can be further extended through the use of macrocells, microcells, picocells -- think access points of various sizes and power that would be installed on a water tower, or outside of a building, or in an office building. The goal is always to get proper coverage as line of sight is one of the best determinants of signal.
Like access points in a WiFi network for an office, all these stations are connected together by the carrier and routed through various technologies. Once you have determined the ideal carrier for your Meraki device, you can proceed to ordering a SIM card and data plan. Many modern phones come with a eSIM that allow a carrier to provision a phone remotely and without needing physical insertion. The eSIM chip on a device takes the place of the physical SIM card. The MG21/21E, Z3C, MX67C, and MX68CW, for example, require a physical nano sized (4FF) SIM card to be inserted.
Each cellular device is identified by a unique 15-digit numeric identifier called the International Mobile Equipment Identity or IMEI. Smartphones, routers, M2M devices — anything with a cellular modem has a unique IMEI that is generated by the modem vendor or the OEM vendor (Cisco Meraki). This is similar to the concept of a MAC addresses for wired interfaces. The first 8 digits of the IMEI is the Type Allocation Code (TAC). It helps identify a vendor and model of the device.
When choosing a carrier and selecting a plan, the carrier will require the IMEI in order to properly identify a compatible data plan. Data plans come with a certain amount of data per pay period and come with various additions such as unlimited texting, phone calls, or in some cases roaming with certain caveats. Roaming allows that SIM card to roam to another network. For example, if you choose AT&T and they fail to have coverage in an area far from home, AT&T would negotiate for the user to allow the plan to roam to T-Mobile.
Once you have been on boarded by the carrier, they will pair the IMEI to that data plan. The IMEI thus acts like an identifier for that device on their network. Meraki devices do not support texting or voice calls through Meraki cellular compatible devices, so carriers will be offering plans which provide data only.
Each SIM card has a unique value called the Integrated Circuit Card Identifier, ICCID. This value is unique across all SIM cards. Providers like AT&T use ICCIDs to know if its a valid SIM card for their network. For example, a T-Mobile SIM card would not be compatible with AT&T’s network.
Carriers will use the ICCID and IMEIs together to link the data plan and device together. Both the ICCID and IMEI dictate what kind of data plan you will receive, i.e. 30GB a month with no text or calling. The ICCID provides validation to the carrier that it is their SIM card and if it is, they will allow you onto their network. There are other special identifiers that this article will cover (e.g. IMSI, MDN) but ICCID and IMEI are generally the two most used values.
Determining Signal Strength
Wireless radio signals are usually measured in dbm, but that's not the case for the wonderful world of cellular. The determination of what is a good signal actually depends on the technology that is being used. Bands dictate which carrier would be compatible with our devices, and CAT is the category modem, which determines how fast the connection can go.
Cellular technology continues to evolve. The current mainstream deployment is the 3GPP standard known as Long-Term Evolution or LTE. This system has evolved from previous system known as Universal Mobile Telecommunication System (UMTS) and before that, the Global System for Mobile Communications (GSM). While these technologies can be a stand alone post by itself, this article is generally focused on LTE.
Two primary variables that can be used to determine “strength” of a 4G LTE signal are the Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ). Once you receive values from these two stats, you will pick the lower of the two values, and convert that into the well known signal “bars” to make it simple to understand at a glance. To keep things simple, the value of each will be in the range of the tables below.
You can think of RSRP as how strongly the signal from the cell tower is 'heard' from the device. Cellular devices will tend to select the strongest signal they hear. RSRQ is used to inform us on how much noise or how much interference the cellular device is experiencing. With high interference, the device may have trouble selecting a good frequency. While there are more detailed technical explanations, the aim here is to understand some values to get a snapshot of the situation. For 3G, the values that would be of interest would be RSCP and Ec/No. For 2G, you would only look at RSSI which is measured in dbm. Because our product is not designed to run on these technologies, we advise making sure your area of deployments have strong 4G LTE coverage for the chosen carrier.
|RSRP Range||RSRQ Range||RSCP||Ec/No|
|5||RSRP >= -83||RSRQ >= -7||RSCP >= -80||EC/NO >= -9|
|4||-83 > RSRP >= -92||-7 > RSRQ >= -10||-80 > RSCP >= -90||-9 > EC/NO >= -11|
|3||-92 > RSRP >= -102||-10 > RSRQ >= -13||-90 > RSCP >= -100||-11 > EC/NO >= -13|
|2||-102 > RSRP >= -111||-13 > RSRQ >= -16||-100 > RSCP >= -106||-13 > EC/NO >= -15|
|1||-111 > RSRP >= -140||-16 > RSRQ >= -20||-106 > RSCP >= -125||-15 > EC/NO >= -19|
When it comes to bands, the internal modem determines what is supported. WiFi technology which has the 2.4ghz and 5ghz band for connectivity, and the cellular world works in a similar manner. Modems have various compatible bands that dictate which frequencies they can use to connect to a cellular network. These usable bands are also further regulated by a local regulatory body.
The chart shows how multiple countries could have some overlapping bands, and also have bands that are particular to a certain country or region. Carriers will be allocated a part of those frequencies and these allocated ranges will determine if your cellular device will be compatible with that carrier.
CAT (UE Category)
The CAT is in reference to the category the device and determines the capability of the underlying hardware. The MG, for example, is a CAT6 device and is thus technically capable up to 300mbps for its download speed. The table below summarizes a couple of the other categories.
The signal strength will determine how good the signal is for the device. The frequency bands determine what carriers our device will be compatible with. And the CAT determines how fast you're theoretically able to go on that carrier if the signal and bands check out.
Configuring Bearer Settings
Access Point Name (APN)
The access point name (APN) is a configuration that is usually done automatically by the device when connecting to a carrier. The APN configuration lets the carrier know what network the device should have access to. So if the device wants data (internet), it must have the correct APN. Depending on the APN, this also may determine whether the device will receive a static IP address on the carrier network. Generally, for these static IP APNs, the carrier will specify a different APN for the device to use.
MVNOs (mobile virtual network operators) like Google Fi, Aeris, and Cricket piggy back off of major carriers and require a separate APN from the major carrier in order to allow access to data services. For example, AT&T uses the APN broadband, Aeris runs on an AT&T network and requires users to configure the APN iot.aer.net in order to enable data services. If left on the default APN broadband with an Aeris SIM card, the data services will not work. Therefore, it is critically important that a SIM card and its data plan be properly paired with the correct APN assigned from the carrier.
For some carriers, additional security measures are needed for the APN. An additional username and password can be required for particular APNs. This allows the carrier to restrict the APN to only authenticated users.
The SIM PIN (Personal Identification Number) is a layer of security that is occasionally enabled on SIM cards. This type of security is to prevent unauthorized users from using the SIM card. PINs are usually 4 numeric digits. If a PIN is entered to many times, it will lock the SIM and would require a PIN Unblocking Key (PUK) to unlock.