Medium access design for LTE in unlicensed band In this paper, a medium access protocol suitably adapted for the operation of Long term evolution (LTE) in unlicensed band (LTE-U) is proposed. The MAC design considers the impact of LTE-U on the devices operating in unlicensed band, such as WiFi and legacy LTE. The LTE-U design differences from the legacy LTE system, an inherently a synchronized, tightly controlled system are explored. The performance of LTE-U is studied via a detailed system level simulator implementation and 3GPP simulation test scenarios. We show that our proposed MAC design enables high throughput in unlicensed band and achieves co-existence with the incumbent systems. Moreover, the use of channel reservation mechanisms is shown to improve LTE-U cell edge performance.