  LTE is increasingly seen as a system for serving real-time Machine-to-Machine
(M2M) communication needs. The asynchronous M2M user access in LTE is obtained
through a two-phase access reservation protocol (contention and data phase).
Existing analysis related to these protocols is based on the following
assumptions: (1) there are sufficient resources in the data phase for all
detected contention tokens, and (2) the base station is able to detect
collisions, i.e., tokens activated by multiple users. These assumptions are not
always applicable to LTE - specifically, (1) due to the variable amount of
available data resources caused by variable load, and (2) detection of
collisions in contention phase may not be possible. All of this affects
transmission of real-time M2M traffic, where data packets have to be sent
within a deadline and may have only one contention opportunity. We analyze the
features of the two-phase LTE reservation protocol and derive its throughput,
i.e., the number of successful transmissions in the data phase, when
assumptions (1) and (2) do not hold.
