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Module 1
Introduction to the GSM Termination Business
What you’ll get:
a clear picture of what GSM termination is,
how VoIP to GSM works end-to-end,
where the real opportunities lie,
and what actually drives profit.
Download Module 1 PDF
Next: Technical Foundations
What GSM termination is and how VoIP to GSM works.
End-to-end flow
(roles of the components):
Definition (plain English):
GSM termination is delivering a VoIP call into a local mobile network via your own GSM gateway + SIMs so the callee receives a normal mobile call. You earn a payout per minute from a traffic buyer; your profit is the spread between this payout and your effective cost per minute.
Caller
The person or dialer app that places the call.
Provides the CLI (caller ID) and media (codec) to the provider.
Hands the call off into VoIP over SIP..
SIP Trunk (VoIP)
A secure IP interconnect from the traffic buyer to your endpoint (IP/domain).
Buyer sends SIP INVITE to your system; you allow-list IPs / auth and negotiate codecs/RTP. Buyer expects stable QoS and clean CDRs.
Softswitch/SBC
Policy & security layer for VoIP.
Normalizes numbers, applies routing
to a specific gateway/SIM group, enforces CPS/CC limits.
Generates CDRs, protects with ACL/TLS/IPsec;
may handle early media (180/183) and transcoding.
GSM gateway:
Converts VoIP to GSM using installed SIMs (GoIP / Skyline / Ejointech).
Selects a SIM/port by rules (prefix, balance, rotation), preserves CLI when required. Controls call setup toward the mobile network and reports channel state/quality.
SIM & BTS (cell tower)
Chosen SIM registers on the BTS;
the call is originated as a normal mobile (MO) call.
Radio quality (RSSI/RSRP) and clean RF reduce PDD and drop rate.
SIM lifecycle matters: registration, rotation, cooling to avoid blocks.
Callee (PSTN/mobile)
The recipient’s phone rings on the public network.
Once answered, voice flows RTP↔GSM via your gateway.
Quality is tracked by ASR/ACD, PDD, MOS; both sides bill from CDRs and resolve disputes via test calls/SLA.
Quality & Route Signals Buyers Watch
KPIs and route context buyers
use to judge your node.
  • ASR & ACD
    Answered-call ratio (ASR) and average call duration (ACD).
    Higher ASR/ACD = healthier demand, fewer disputes, more stable volumes.
  • PDD
    Post-Dial Delay — time from dialing to ring/answer.
    Keep it low to improve answer rates and user experience.
  • CLI
    Caller ID presentation.
    Required by many buyers; clean, consistent CLI usually commands better price.
  • MOS (Voice quality)
    Perceived audio quality (MOS) depends on jitter, packet loss and codec.
    Track RTP stats and keep network clean to avoid degradations.
  • Route & traffic types
    CLI vs non-CLI affects demand and payout.
    Retail vs wholesale have different quality expectations, dispute rules, and stability.
  • Myths vs reality
    Myth: “Only hardware matters.” → Ops discipline (monitoring, SIM lifecycle, risk control) drives profit.
    Myth: “Any country is the same.” → SIM/KYC, logistics, power/network vary widely by region.
Market overview
Opportunities differ by region—align payout potential, SIM/KYC policy, logistics & power, and your ability to keep QoS stable.
AFRICA
  • Strong wholesale demand; attractive payouts on solid CLI routes.
  • SIM/KYC rules can be strict; sometimes local presence/agreements are needed.
  • Power and last-mile links vary—plan UPS, backup ISP/LTE, quality antennas.
  • Import/customs and IMEI/registration policies may add lead time and cost.
  • Best fit: if you can ensure uptime and follow local SIM rules with a reliable local partner.
Asia
  • Very large, diverse markets with dense urban coverage; rates are competitive.
  • Compliance/KYC can be stricter; expect documentation and usage-pattern controls.
  • Tariffs and FUPs differ by operator; watch thresholds that trigger SIM scrutiny.
  • Gear is easier to source locally; network quality is usually strong in cities.
  • Best fit: if you run tight documentation, clean CLI, and disciplined QoS.
Latin America
  • Consistent payouts on quality routes; once stable, scaling is predictable.
  • Customs/duties and shipping times vary widely by country—plan spares ahead.
  • Residential power/ISP can be inconsistent; prefer FTTH + LTE failover.
  • SIM registration typically required; policies differ per operator.
  • Best fit: if you can plan procurement, maintain QoS, and secure reliable hosting
Your first country
  • Start with wide payout − cost spread and realistic compliance/logistics.
  • Verify site basics: stable power + internet, room for antennas, secure space.
  • Ensure supply chain: trusted equipment and SIM sources + spares.
  • Line up 1–2 reliable buyers; run a 7-day test with clear SLA & CDR evidence.
  • Model economics: break-even minutes, sensitivity ±10% payout, plan to add a second node when stable.
Profit & Unit Economics
Calculate margin and payback with a simple model. See which levers actually change results.
  • Core formula
    Gross Margin = (Payout/min − Effective Cost/min) × Billable Minutes.
    Everything in the business rolls up to these three variables.
  • Payout per minute
    The rate your buyer pays. Improve it by keeping clean CLI, good ASR/ACD, and reliable delivery; negotiate after a stable test period.
  • Effective cost per minute
    Your real cost to originate a minute: SIM plan, connectivity (ISP/VPN/IPsec), power/UPS, hardware depreciation (gateway/SIM server/antennas), and ops overhead (spares, space, maintenance).
  • Utilization & uptime
    More stable minutes/day = more margin. Control CPS/CC, prevent incidents, use monitoring/alerts and simple runbooks to reduce downtime.
  • Quality & disputes
    Buyers watch ASR, ACD, PDD, CLI, MOS. Keep test calls and CDRs; agree a lightweight SLA to avoid revenue loss in disputes.
  • Risk & compliance to include in the math
    Local regulation & SIM/KYC, SIM lifecycle/blocks, traffic-fraud patterns (short-stopping/refiling/CLI tampering), and power/ISP failures. Plan mitigations and budget for them.
Download sample P&L
Illustrative scenario for 12,000 daily minutes
(e.g., GOIP-8 at moderate load)
*for orientation only
Actual results depend on country, SIM/KYC, logistics, and how well you maintain QoS.
  • $0.035
    Payout /min
  • $0.018
    Effective cost /min
  • $204
    Gross/day: (0.035 − 0.018) × 12,000
  • $6,120
    Gross/month (×30)
Quick glossary
(for consistent wording across the course)
  • ASR: Answer-Seizure Ratio (% answered).
  • ACD: Average Call Duration (avg length of answered calls).
  • PDD: Post-Dial Delay (dial → ring/answer).
  • CLI: Caller ID presentation.
  • MOS: Mean Opinion Score (voice quality).
  • SIP trunk: IP connection for VoIP minutes.
  • Gateway: Device that originates calls into the mobile network using your SIMs.
  • CDR: Call Detail Records (billing/quality evidence).
  • BTS: Base Transceiver Station (cell tower).
How Module 1 works
From concepts to real-world choices—everything you need to see the full picture.
Step 1 — Business model
What GSM termination is, how you earn, and where margin comes from.
Step 2 — End-to-end flow
SIP trunk → Softswitch/SBC → GSM gateway → SIM/BTS → Callee.
What each piece does and how QoS is measured (ASR/ACD/PDD/CLI/MOS).
Step 3 — Market map
Signals & constraints in Africa, Asia, LatAm; principles to pick your first country.
Step 4 — Profit engine
Formula: (Payout − Cost) × Minutes. What drives results: quality, uptime, costs, buyer mix.
Download detailed syllabus (PDF)