WLAN roaming

What is WLAN roaming and how to make roaming for voice in WLAN networks smooth?

Roaming in WLAN (also in GSM networks) is associated with physical movement and connectivity while movement.

You could apply following terms to roaming in WLAN networks:

1. Pre-call roaming.
When user moves before making a call. This movement could occur between Layer 2 and Layer 3 boundaries. In Layer 3 roaming phone will change its IP address.

2. Mid-call roaming.
When user moves with active call.



So as I said before, we could divide device roaming on:

1. Layer 2 roaming
Layer 2 roaming occurs when station (PC or wireless IP phone) moves from one access point to other. Both access points are on the same IP subnet, so station doesn’t have to change its IP address.

2. Layer 3 roaming
Layer 3 roaming occurs when client moves from one access point to another. This two access points works on different IP subnets. So phone will have to change its IP address. Problem with changing IP address is that its voice calls or data sessions will drop.

So when you are designing your network you have to be aware of Roaming restrictions, especially Layer 3 roaming.



If you are expert in wireless and want find out more about Roaming in wireless networks check this book - Roaming in Wireless Networks. It covers not only WLAN, but also CCS7, GSM, GPRS, 3G.

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