Consider two co-channel cells using frequency F₁ separated by a distance D. If each cell has a radius R then the ratio q=D/R governs the design of the handoff mechanism. Other frequency channels F₂, F₃ and F₄  can be used to fill in the co-channel cells in order to provide communication system for the whole area. The fill in frequencies F₂, F₃ and F₄  are also assigned to the corresponding cells C₂, C₃ and C₄ according to the same value of q. If a mobile unit starts a call in cell C₁ and moves into cell C₂ . Then the call can be dropped and reinitiated in the frequency channel from F₁ to F₂ while the mobile unit moves from C₁ to C₂. This process of changing frequencies is done automatically by the system and is referred to as handoff.

For implementing a mobile network, a handoff mechanism must be defined to maintain uninterrupted user communication session during his/her movement from one location to another. Handoff mechanism handles subscriber station (SS) switching from one Base Station (BS) to another. Different handoff techniques have been developed. In general, they can be divided into soft handoff and hard handoff.

Soft handoff is used in voice-centric cellular networks such as GSM or CDMA. It uses a make-before-break approach whereas a connection to the next BS is established before a subscriber station SS leaves an ongoing connection to a Base Station BS. This technique is suitable to handle voice and other latency-sensitive services such as Internet multiplayer game and video conference. When used for delivering data traffic (such as web browsing and e-mail), soft handoff will result in lower spectral efficiency because this type of traffic is bursty and does not require continous handover from one Base Station BS to another.

A Hard handoff, also known as Break-before-Make, is employed by first disconnecting with the base station before switching to another base station in a communication network. This type of handoff mechanism is particularly suitable for delay-tolerant communications traffic such as broadband technology-enabled Internet, VoIP, or mobile networking technology such as WiMax. A Hard handoff is less expensive to implement compared to soft handoff and is generally more spectral (network bandwidth) efficient, particularly, in heavy data traffic environments but it causes longer delay. A network-optimized hard handoff mechanism was developed for Mobile WiMAX to keep a handoff delay under 50 ms.