LTE Random Access

The Random Access Channel (RACH) is defined by 3GPP as an uplink, contention based, common transport channel. It is typically used for random access transmissions and the transport of control information such as to register the terminal to the network after power-up, to perform an location update after moving from one location area to another, or to initiate a call by setting up a connection from the User Equipment (UE) to the Node-B. In current UMTS standard, RACH can also be used to send small amount of data on the uplink, which is quite different from the approach taken by 3GPP. Due to the orthogonal uplink in LTE a specific resource must be reserved to avoid interference to other users in the cell. In LTE no other information in addition to information provided by the preamble ID can be send. This keeps that non-orthogonal resource at a minimum.

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