Building a small private cellular network is now within reach for labs, campuses, hobbyist testbeds, industrial sites, and research projects. With accessible radio hardware, programmable SIM cards, and open-source core network software, you can create a controlled LTE or 5G environment for data connectivity, device testing, IoT deployments, or learning how mobile networks work from the inside.
A private cellular system combines a radio access network, a core network, SIM-based authentication, IP routing, and user equipment such as phones or modems. The basic idea is simple: your radio equipment provides the cell signal, your core network authenticates subscribers and assigns connectivity, and your SIM cards identify which devices are allowed to attach.
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Before transmitting anything over the air, spectrum rules and safety requirements must come first. The practical path is to use licensed spectrum you control, a shared or lightly licensed band where permitted, a shielded RF environment, or cabled test setups that prevent unintended emissions. From there, the project becomes a structured build: choose hardware, install the core, provision SIMs, connect devices, test performance, and secure the network.
Cellular Network Architecture and Core Components
A private cellular network has the same basic shape as a public mobile network, just at a smaller scale. User equipment, such as phones, modems, routers, or IoT modules, connects over radio to an access network. That access network forwards signaling and user traffic to a core network, which authenticates SIM cards, assigns IP addresses, applies policy, and routes traffic to local services or the internet. In a lab or campus deployment, these functions may all run on one server, while the radio hardware sits nearby with antennas placed for the desired coverage area.
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For LTE, the radio side is called the E-UTRAN and is typically represented by an eNodeB. The LTE core is the EPC, made up of functions such as the MME for mobility and attach signaling, the HSS for subscriber records and authentication data, the SGW and PGW for user-plane forwarding, and the PCRF for policy control. Open-source projects often combine several of these into fewer services so they are easier to deploy. For example, a small Open5GS or similar installation can run the control plane, subscriber database, and packet gateway on one Linux machine, then connect to an SDR-based eNodeB or a commercial small cell.
For 5G, the naming changes and the architecture becomes more service-oriented. The radio is the gNodeB, and the 5G core includes components such as the AMF for registration and mobility, the SMF for session management, the UPF for user-plane traffic, the AUSF and UDM for authentication and subscriber data, and the NRF for service discovery. In small private networks, the UPF is especially relevant because it determines where device traffic exits: directly to a local application server, into an enterprise LAN, through a firewall, or out to the public internet.
Main building blocks
- User equipment: Phones, USB modems, industrial routers, cameras, sensors, or test devices with SIM or eSIM support.
- SIM credentials: Subscriber identifiers and cryptographic keys, usually including IMSI, Ki, and operator parameters such as MCC and MNC.
- Radio access network: An SDR with radio software or a dedicated small cell that transmits LTE or 5G signals and handles low-level radio scheduling.
- Core network: Software services that authenticate devices, manage sessions, allocate IP addresses, and route traffic.
- Backhaul network: Ethernet, fiber, or IP transport between the radio unit and the core, often on a private VLAN or isolated lab subnet.
- Operations layer: Logging, metrics, packet capture, dashboards, configuration management, and alerting.
The split between the radio and the core is one of the most useful design choices. With an SDR, the same host may run both the radio stack and part of the core during experimentation, but timing, CPU load, and USB bandwidth can become tight. With a small cell, the radio vendor appliance usually handles the physical layer and much of the access network behavior, while your server runs only the core. This approach is often more stable for mulle phones, mobility testing, and longer-running demonstrations.
Data traffic follows a clear path. A phone attaches to the cell, the core checks its SIM credentials against the subscriber database, and the device receives an IP address. When the phone opens a web page or connects to a private application, packets travel from the phone to the radio, through a tunnel such as GTP-U, into the gateway or UPF, and then onward to the selected network. Voice can be handled as packet data through IMS and VoLTE, but that adds another set of services and device compatibility constraints, so many first deployments start with data-only LTE or 5G before adding calling and messaging.
Legal, Spectrum, and Safety Requirements
Before powering any radio hardware, treat the network as a regulated transmitter rather than a normal Wi-Fi lab. Cellular bands are licensed in most countries, and transmitting LTE, 5G NR, GSM, UMTS, or NB-IoT signals without authorization can interfere with public mobile operators, emergency services, aviation systems, railway communications, or other protected users. A safe private cellular build starts with a written plan: frequency range, bandwidth, transmit power, antenna type, indoor or outdoor use, site location, and the exact equipment model. That plan determines whether you can use a shared band, apply for a license, lease spectrum, operate under an experimental authorization, or restrict testing to a shielded environment.
Regulations vary by country, but the common rule is simple: do not radiate on public cellular bands unless you have explicit permission. In the United States, options may include CBRS in the 3.5 GHz band through a Spectrum Access System, experimental licensing through the FCC, or work inside a properly shielded RF enclosure. In parts of Europe, local private network licenses may be available in bands such as 3.8–4.2 GHz, depending on the regulator. Some regions provide shared or local industrial spectrum for campuses, factories, ports, farms, and research sites. Unlicensed bands are generally not a shortcut for standard cellular operation, because mobile technologies have strict emission masks, power limits, and coexistence requirements that may not match ordinary unlicensed rules.
Practical compliance checklist
- Identify the band and channel bandwidth: confirm the exact uplink and downlink frequencies your radio will transmit, not just the nominal LTE or NR band number.
- Check authorization: obtain a local license, CBRS grant, spectrum lease, lab authorization, or use a shielded box with conducted RF paths.
- Limit transmit power: start at the lowest usable gain, especially with SDRs, power amplifiers, and active antennas.
- Control the antenna system: use indoor antennas, attenuators, dummy loads, filters, and RF enclosures to prevent unintended coverage.
- Avoid live operator bands: scanning is different from transmitting; never assume a quiet-looking channel is available.
- Document settings: keep records of EARFCN or ARFCN, PCI, PLMN, TAC, power levels, antenna placement, and test dates.
Lab containment is often the cleanest path for early development. A cabled setup can connect the SDR or small cell to a phone through attenuators, a programmable RF shield box, or test SIM devices with antenna ports. This reduces interference risk and makes experiments repeatable. For over-the-air testing, use low-gain antennas, keep the cell indoors, choose a site with physical isolation, and verify with a spectrum analyzer or calibrated scanner that the signal does not extend beyond the intended area. If you add amplifiers, band-pass filters become essential, since SDRs and inexpensive radio modules can produce unwanted emissions outside the selected channel.
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Safety also includes RF exposure, electrical safety, and equipment integrity. Small indoor cells usually operate at modest power, but antennas should still be mounted away from people who may remain near them for long periods. Follow the exposure limits published by the relevant regulator or standards body, account for antenna gain, and avoid improvised high-power transmit chains. Use properly rated power supplies, grounding where required, weatherproofing for outdoor hardware, and surge protection for mast-mounted antennas. Treat SIM credentials and subscriber identifiers as sensitive operational data, since a misconfigured test network can cause confusing device behavior or accidental attachment attempts from nearby phones if the PLMN and radio parameters overlap with real networks.
Hardware Options: SDRs, Small Cells, Antennas, and SIM Cards
The radio side of a private cellular network can be built in two main ways: with a software-defined radio running an open-source base station stack, or with a purpose-built small cell that speaks standard telecom interfaces to your core network. The right choice depends on whether your goal is learning and experimentation, indoor lab coverage, or a more stable private LTE/5G deployment. You also need antennas matched to the band you are using, a timing source if required by the radio, and programmable SIM cards with credentials that match your core network database.
SDR-based radio access
Software-defined radios are popular for lab networks because they are flexible and well supported by projects such as srsRAN and OpenAirInterface. Common choices include the Ettus USRP B200/B210, USRP N310, LimeSDR, and bladeRF. For a basic LTE lab cell, a USRP B210 is a frequent starting point because it supports full-duplex operation, has enough bandwidth for small LTE carriers, and works over USB 3.0. Lower-cost SDRs can be useful for receive-only testing or narrow experiments, but they may struggle with stable transmit performance, clock accuracy, and duplex operation.
An SDR setup usually needs a host machine with a strong CPU, reliable USB or Ethernet connectivity, and a Linux distribution supported by the RAN software. For LTE, the computer runs the eNodeB software and connects to the EPC over interfaces such as S1. For 5G standalone, it runs the gNodeB and connects to a 5G core over NG interfaces. Clocking matters: some radios can use their internal oscillator for a small isolated lab, while more demanding setups may require a GPS-disciplined oscillator, 10 MHz reference, or PPS input to keep timing stable.
Small cells and integrated radios
A small cell is closer to commercial cellular equipment. It combines the radio, baseband processing, and management functions in a compact appliance, often designed for indoor coverage. LTE small cells may expose S1 interfaces toward an EPC, while newer 5G units may support NG interfaces toward a 5G core. Some devices are locked to a vendor cloud or mobile operator configuration, so verify that the unit supports local management, configurable PLMN values, custom TAC settings, and connection to your chosen open-source core before buying used hardware.
| Option | Best fit | Typical tradeoff |
|---|---|---|
| USRP-class SDR | LTE/5G research, repeatable lab work | Higher cost, more host tuning |
| Budget SDR | Learning RF concepts and limited experiments | Lower stability and weaker duplex support |
| Enterprise small cell | Reliable indoor private coverage | May be vendor-locked or hard to reconfigure |
Antennas, filters, and RF accessories
Use antennas designed for the exact frequency range you are authorized to operate in. A mismatched antenna reduces coverage and can stress the transmitter. For a controlled lab, low-gain omnidirectional antennas and very low transmit power are usually enough. If testing on a bench, attenuators, coaxial cables, and shielded enclosures are safer than radiating into open space. Band-pass filters can reduce unwanted emissions, and a spectrum analyzer or calibrated receiver helps confirm that the signal stays within the intended channel.
SIM cards and user devices
Phones and modems authenticate to the network using SIM credentials, so you need programmable SIMs and a reader/writer. Common lab SIMs include sysmoISIM-SJA2, programmable USIM/ISIM cards, or vendor test SIMs. Each SIM must have an IMSI, authentication key, operator code, and related parameters that match the subscriber entry in your core network. For LTE, the USIM profile is usually sufficient. For 5G standalone, ISIM or properly configured USIM support may be needed depending on the device and core configuration.
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User equipment can be a smartphone, LTE USB modem, embedded cellular module, or industrial router. Pick devices that support your chosen radio band, duplex mode, and network generation. Many consumer phones hide useful diagnostics, so an Android device with engineering menus or a cellular modem with AT command access can make testing easier. Keep a simple inventory of each SIM, IMSI, assigned device, radio band, and allowed services; this avoids confusion once you begin provisioning subscribers and testing attach, data sessions, SMS, or voice features.
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The cellular core is the software side of your private network: it authenticates SIMs, assigns IP addresses, routes user traffic, and manages sessions between phones and the radio access network. For a small lab or campus build, common open-source choices include Open5GS, free5GC, and srsRAN Project. Open5GS is widely used for LTE EPC and 5G core experiments, free5GC focuses on 5G standalone networks, and srsRAN can pair a software core with its SDR-based RAN components. Pick the core that matches your radio equipment: LTE eNodeB equipment needs an EPC, while 5G gNodeB equipment may use a 5G core, depending on whether it runs standalone or non-standalone mode.
A typical small deployment runs the core on a Linux server, mini PC, or virtual machine with a stable wired Ethernet connection to the radio. Ubuntu LTS or Debian is usually the easiest base because package dependencies, documentation, and community examples are widely available. Allocate at least two network interfaces if possible: one for management and one for the radio/user-plane side. In an LTE Open5GS-style layout, the main services include the MME for mobility management, HSS/UDR-style subscriber data, SGW/PGW for user traffic, and PCRF/PCF policy functions. In 5G, the same responsibilities are split across AMF, SMF, UPF, AUSF, UDM, and related services.
Basic setup flow
- Install prerequisites: update the operating system, set a static IP address, enable NTP time synchronization, and install database and packet-routing dependencies such as MongoDB, iproute2, and firewall tooling.
- Install the core: use the project’s packages, containers, or source build. Packages are simplest for a persistent lab network; containers are useful when you want repeatable test environments.
- Configure network identities: set the MCC and MNC values, TAC, PLMN, APN/DNN names, and IP ranges for user equipment. These values must match the SIM profiles and radio configuration.
- Configure interfaces: bind control-plane services to the address reachable by the eNodeB or gNodeB, and bind the user-plane gateway to the interface that will carry phone data.
- Enable forwarding and NAT: turn on IPv4 forwarding and add firewall or nftables rules so connected phones can reach the internet or your private services.
- Start and verify services: check systemd logs, container logs, or web dashboards to confirm that each network function is running and listening on the expected ports.
For LTE, the radio usually connects to the core over the S1 interface: S1-MME for signaling and S1-U for user traffic. For 5G standalone, the gNodeB connects using N2 signaling toward the AMF and N3 user-plane traffic toward the UPF. If the radio fails to attach, check the PLMN, TAC, local IP binding, SCTP reachability, and firewall rules first. A mismatched MCC/MNC or an unreachable control-plane address is one of the most common causes of registration failure.
| Core choice | Best fit | Common deployment style |
|---|---|---|
| Open5GS | LTE EPC, 5G SA labs, mixed learning environments | Linux packages, source build, or containers |
| free5GC | 5G standalone research and testing | Source build or containerized services |
| srsRAN Project | SDR-based LTE/5G experimentation | Integrated lab stack with SDR radio components |
Once the core is reachable from the radio, add a simple data network behind it. This can be ordinary internet access through NAT, an isolated lab subnet, or a private application server for testing. Use clear address ranges, such as a dedicated UE pool like 10.45.0.0/16, and avoid overlapping with your management LAN. Keep logs enabled during early testing, especially for authentication, session creation, and user-plane forwarding. These logs will become essential when you provision SIMs and begin attaching real phones or modems to the network.
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Provisioning SIMs and Connecting User Devices
After the radio access network and core are running, each phone, modem, or test handset needs a subscriber identity that the core recognizes. In a private LTE or 5G lab this usually means programmable SIM cards, such as sysmoUSIM, OpenCells-compatible UICCs, or other test SIMs that expose the IMSI and cryptographic keys. The core network database must contain the same subscriber values that are written to the SIM, otherwise authentication will fail and the device will keep searching, reject the network, or attach briefly and drop.
The central fields are the IMSI, Ki, OP or OPc, and the allowed services for that subscriber. The IMSI identifies the subscriber and normally starts with the MCC and MNC you configured in the radio and core. In a lab you might use test network codes where permitted by your jurisdiction, while production deployments require assigned codes. The Ki and OPc are secret authentication values shared only by the SIM and the subscriber database. They should be generated uniquely per SIM, stored carefully, and never reused across a fleet of devices.
Typical SIM provisioning workflow
- Choose the PLMN values: Use the same MCC and MNC across the core, eNodeB or gNodeB, and SIM profiles.
- Create subscriber records: Add IMSI, Ki, OPc, APN or DNN, allowed slice if using 5G, and service permissions in your core’s web UI, database, or CLI.
- Program the SIM: Use a compatible USB smart-card reader and vendor tooling to write IMSI, Ki, OPc, SMSC if needed, and preferred network lists.
- Label and track cards: Keep a simple inventory that maps each SIM ICCID to its IMSI, assigned device, and test purpose.
- Insert and configure the device: Add the SIM to the handset, router, or modem, then set the APN or DNN expected by the core.
For data-only LTE, the device usually needs a matching APN such as internet, private, or a name defined in the packet core. Many Android phones allow this under mobile network settings; USB modems often need AT commands or a vendor dashboard. For 5G standalone, the equivalent data network name and slice configuration must align with the subscriber profile. If VoLTE is part of the experiment, the handset also needs IMS registration parameters, compatible firmware, and an IMS core or suitable test implementation. Many consumer phones hide IMS settings, so data testing with phones or industrial LTE routers is usually simpler than voice testing.
| Field | Where it appears | Common mismatch symptom |
|---|---|---|
| IMSI | SIM and core subscriber table | Authentication reject or unknown subscriber |
| MCC/MNC | SIM, core, and radio configuration | Device does not select the network |
| Ki and OPc | SIM and authentication database | Attach attempt fails during authentication |
| APN or DNN | Device settings and core policy | Attach succeeds but data session fails |
Once provisioned, connect a user device by scanning for networks or setting manual network selection if the phone does not automatically camp on your cell. Confirm that the PLMN shown by the phone matches your configuration, then watch the core logs for registration, authentication, security mode setup, and session establishment. A successful attach or registration should result in an assigned IP address, an active bearer or PDU session, and visible traffic on the user-plane interface. If the device sees the cell but refuses to join, check band support, SIM credentials, PLMN selection, and whether the handset is locked to a commercial carrier.
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Once the core network, radio access equipment, and SIM profiles are in place, test the network in small, controlled steps. Start with one known-good handset or modem, one provisioned SIM, and a short antenna distance before expanding to mulle devices or wider coverage. The first goal is not maximum speed; it is proving that the radio cell is visible, the device can attach, authentication succeeds, an IP address is assigned, and traffic reaches the intended data network.
Initial attach and registration checks
Begin by confirming that the user device sees the private network identifier you configured, such as the PLMN, MCC/MNC, or network name. On the core side, watch the logs for registration, authentication, security mode setup, session creation, and bearer establishment. In LTE, this means checking MME, HSS, SGW, PGW, and eNodeB activity. In 5G SA, check AMF, AUSF, UDM, SMF, UPF, and gNodeB activity. A failed attach is usually caused by mismatched IMSI, Ki/OPc values, unsupported bands, incorrect APN/DNN settings, or poor RF conditions.
- Cell visibility: the handset can see the configured PLMN and radio band.
- Registration: the SIM authenticates successfully against the subscriber database.
- Session setup: the device receives an IP address and default route.
- Data path: packets pass through the user-plane gateway to the target LAN or internet uplink.
Coverage and RF validation
Measure coverage before increasing transmit power or adding antennas. Walk the intended service area with a phone field-test screen, cellular scanner, or modem reporting tools and record RSRP, RSRQ, SINR, and handover behavior if more than one cell is active. For a bench network, use attenuators, shield boxes, or very low transmit power to avoid unintended radiation. For a room-scale network, map signal quality near walls, metal racks, windows, and machinery, because reflections and obstruction can create sharp dead zones even when the cell appears strong nearby.
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| Ping and jitter | Latency stability | Validate interactive traffic and voice |
Throughput, latency, calls, and SMS
For data testing, run controlled uplink and downlink tests with tools such as iperf3 between the user device and a server on the local network. Test downlink, uplink, bidirectional traffic, small-packet latency, and longer sustained transfers. Compare results against the radio configuration: channel bandwidth, MIMO capability, modulation, device category, backhaul capacity, and CPU load on the core. If throughput is far below expectation, check RF quality first, then inspect MTU settings, NAT rules, user-plane routing, SDR sample drops, and small-cell backhaul limits.
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Voice testing depends on the services you implemented. A data-only LTE or 5G network will not provide ordinary mobile calling unless you add IMS, VoLTE support, compatible handsets, and the correct SIM and APN profiles. For many private networks, push-to-talk, SIP over data, or application-layer calling is simpler than full carrier-style voice. If you do deploy IMS, test registration, emergency-call restrictions, codec negotiation, call setup time, handover behavior, and audio in both directions. SMS also requires explicit support in the core and device configuration; do not assume it works just because packet data works.
Repeatable test plan
- Attach one device and confirm successful authentication in the core logs.
- Verify IP assignment, DNS behavior, routing, and firewall rules.
- Run ping tests to the gateway, local server, and external destination if internet access is enabled.
- Measure uplink and downlink throughput with a local iperf3 server.
- Walk the coverage area and record RSRP, RSRQ, SINR, and dropouts.
- Add more devices gradually and repeat latency and throughput tests under load.
- Test voice, SMS, or application services only after basic data is stable.
Keep every test result tied to a specific configuration: radio band, bandwidth, transmit power, antenna placement, core software version, subscriber profile, and device model. This makes troubleshooting much faster when a later change breaks attachment, reduces throughput, or creates coverage gaps. A small private cellular network is easiest to improve when each measurement can be traced back to a known hardware and software state.
Security, Monitoring, and Operational Limits
Once phones can attach, pass data, and complete basic service tests, treat the private cellular network as production infrastructure rather than a lab toy. A small LTE or 5G setup still handles subscriber identities, authentication keys, traffic metadata, IP routing, and radio access, so weak defaults can expose users or destabilize nearby systems. Lock down the core network host first: run it on a dedicated machine or VM, keep the operating system patched, restrict management ports with a firewall, and require SSH keys instead of passwords. If the web UI, database, metrics dashboard, or packet gateway is reachable from a wider LAN, place it behind a VPN or a reverse proxy with strong authentication.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsSubscriber data deserves special care. IMSI values, Ki/K/OPc keys, and APN assignments should be stored in a controlled location with backups encrypted at rest. Avoid sharing SIM programming CSV files through chat or email, and rotate test credentials when a SIM is lost or handed to another user. For LTE, confirm that mutual authentication is working and that devices are not being accepted with placeholder keys. If the core supports mulle APNs or network slices, separate administrative devices, general test handsets, and IoT equipment into different IP ranges so firewall policies can limit lateral movement.
Monitoring and logs to keep enabled
- Attach and registration events: track IMSI/SUPI, assigned IP address, cell ID, reject causes, and authentication failures.
- Radio metrics: watch RSRP, RSRQ, SINR, PRB usage, retransmissions, handover attempts, and uplink noise floor.
- Core service health: monitor AMF/MME, SMF/SGW-C, UPF/PGW-U, HSS/UDM, database, and DNS availability.
- Traffic counters: record per-subscriber throughput, session duration, packet drops, NAT table pressure, and backhaul utilization.
- Clock and timing status: alert on GPSDO loss, PTP drift, or sample clock instability, especially with SDR-based radios.
Prometheus, Grafana, syslog, journald, and packet captures are usually enough for a small deployment. Keep packet captures targeted and time-limited, since full captures can contain user data and grow quickly. For troubleshooting, capture on clear internal interfaces such as S1/N2, S1-U/N3, SGi/N6, and management links, then remove or encrypt the files after analysis. On the radio side, record configuration changes such as EARFCN/NR-ARFCN, bandwidth, transmit gain, TAC, PLMN, and cell identity so test results can be reproduced.
Practical operating limits
A home-built cellular network has limits that commercial networks hide with dense planning, licensed spectrum, hardened hardware, and full-time operations teams. SDR-based eNodeB or gNodeB setups may support only a few stable users, modest throughput, and limited mobility. USB bandwidth, CPU scheduling, RF front-end linearity, oscillator accuracy, and antenna placement can all become bottlenecks before the core software does. Small cells are usually more stable, but they may require vendor firmware, approved bands, GPS lock, power calibration, and configuration access that is not always documented.
| Area | Common limit | Mitigation |
|---|---|---|
| Coverage | Indoor walls, low antenna height, and low transmit power reduce range. | Use suitable antennas, measure signal quality, and keep emissions within authorization. |
| Capacity | Few radios and narrow channels constrain active users and throughput. | Limit test devices, shape traffic, and choose realistic bandwidth settings. |
| Reliability | SDR timing, host load, and software crashes can interrupt service. | Use stable clocks, process supervision, UPS power, and tested release versions. |
| Mobility | Single-cell networks cannot test real handover behavior. | Add a second synchronized cell only when spectrum permission and timing are controlled. |
Define boundaries before inviting other users onto the network: allowed devices, test hours, data retention period, emergency calling status, and contact procedures if the system misbehaves. Do not present the network as a replacement for public mobile service unless lawful emergency calling, availability, lawful access obligations, and operator responsibilities have been addressed. For most builders, the safest long-term model is a controlled lab or campus testbed with low power, documented configuration, monitored health, and a clear plan to shut down quickly if interference, authentication issues, or unexpected traffic patterns appear.
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Frequently Asked Questions
Can I legally run a private cellular network at home or in a lab?
Only if you operate in spectrum you are authorized to use, or inside a properly shielded test environment. In many countries, transmitting LTE or 5G on licensed cellular bands without permission is illegal even at low power. Practical options include CBRS in the United States, local private-network licenses where available, working with a licensed operator, or using cabled RF/shield boxes for lab testing.
What hardware do I need for a small private LTE or 5G network?
At minimum, you need a radio access device, antennas or RF cabling, a server for the core network, programmable SIM cards, and compatible phones or modems. For experiments, SDRs such as USRP-class devices are flexible but require more tuning and Linux experience. For more reliable service, a used or development small cell is usually easier, provided it supports your chosen band and can connect to an open-source core.
Which open-source core network software should I use?
Open5GS is a common choice for private LTE and 5G core deployments because it is well documented and works with many lab setups. srsRAN can provide both RAN components and core-related tooling, especially for SDR-based systems. For a first build, many readers start with LTE EPC using Open5GS, then move to 5G SA once they understand SIM provisioning, APNs, routing, and radio configuration.
How do I get phones to attach to my private network?
You need programmable SIMs with credentials that match entries in your core network database, including IMSI, Ki, OPC or OP, and APN settings. The phone must support the radio band, duplex mode, and network type you are transmitting, and it may need manual network selection if your network is not a commercial carrier. If the device sees the network but will not attach, check the PLMN, TAC, authentication values, APN, and whether the phone rejects unknown or test networks.
What performance should I expect from a DIY cellular network?
Throughput and coverage are usually far below commercial networks because lab SDRs, small antennas, limited spectrum, and indoor RF conditions constrain performance. A basic LTE lab may support data sessions, pings, and modest throughput, while voice calling requires IMS or VoLTE support and additional configuration. The most realistic goals are learning, device testing, private IoT connectivity, and controlled coverage over a room, lab, or small site.
Bottom Line
Building your own small cellular network is realistic if you keep the scope modest: start with a lab setup, use open-source core software, provision your own SIMs, and connect either an SDR-based radio or a compliant small cell. The key decisions are spectrum authorization, radio hardware, EPC/5GC configuration, and whether your goal is learning, testing IoT devices, or serving a controlled private site.
Your next step is to map the network on paper, confirm what spectrum you can legally use, then deploy a minimal core and one radio before adding users or coverage. Treat security, monitoring, and power/radio planning as part of the build from day one, and scale only after the first phones or devices attach reliably and pass data as expected.
Quick Recap
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