How Roaming Works - A Layman's Explanation


New member
HoFo Member
Aug 9, 2008
Every network broadcasts 2 codes - a country code and a network code. Canada country code is 302 and Mobilicity network code is 320.

A phone "knows" its own home network - because the SIM card tells it this number for the home net. Example, a mobi SIM card "tells" the phone - to expect "302 - 320" network number, and this is the home network. The phone searches for THIS first. If it doesnt find this network, then it searches other networks and compares them against the SIM card's "preferred roaming partners". Rogers number is "302 - 720", and the SIM card lists this network as a "preferred roaming partner "CDN Roaming". The phone connects to this.

What happens if a network is found which is not in the preferred roaming list? The phone attempts to connect to it int he last priority (after trying to find "Home" and "preferred roaming"). The phone "knows" networks are roaming by comparing these numbers. Here is a list of numbers for networks in North America:

Mobilicity: 302 - 320
Wind: 302 - 490
Bell/Telus: 302 - 880
Rogers: 302 - 720
T-Mobile USA: 310 - 260
AT&T USA: 310 - 410

A full list here:


How you are charged on Roaming:

Lets say you are roaming - outside the home zone. Essentially, you are using Rogers network (CDN Roaming). However, when you use Rogers network, you have to compensate them right? So, essentially, you compensate Rogers 20 cent/min for using their network for voice, 10 cent per sms, and $1.50/MB for data.

However, many providers like the big 3 charge you 20 cent for compensation of roaming partners network + your normal fees. Example, normally if a call to US is 25 cent/min, on roaming you pay 20 cent + 25 cent. Mobilicity does not do this. When you roam - they charge you ONLY for roaming partners' network charges.
Good guide. Very helpful. Thanks.

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