Methods and systems of asynchronous access and synchronous transmission include transmitting an initial reservation packet using a first protocol to prevent other devices that use the first protocol from transmitting during a reserved duration. A carrier using a second protocol is activated. Information is transmitted using a second protocol during the reserved duration. During a last subframe of the reserved duration, an additional reservation packet is transmitted using the first protocol to extend the reserved duration. The transmission of the additional reservation packet takes place while the carrier using the second protocol is still active.