 static beam patterns caused by coherent transmission from two antennas. 11.1.2.2.3 Uplink Pilots In an FDMA-based multiuser scenario, each RB can be allocated to a different user in the uplink. Therefore, the pilot structure was defined locally within each RB. For the case of spatial multiplexing in the uplink, the multiple transmit antennas have to use orthogonal pilot patterns to be distinguishable. Due to the fact that one pilot in the short block (SB) represents every second subcarrier in the long block (LB), the choice of 25 SCs per RB is unfavorable (meanwhile, standardization has decided on 12 subcarriers per RB, which corresponds to exactly 6 subcarriers in the SB). Considering this, we combined two RBs of 25 subcarriers each to a double RB, which is considered in the resource allocation scheduler. The uplink resource unit comprises six LBs (i.e., OFDM symbols with 2,048 subcarriers) and two SBs (i.e., OFDM symbols with 1,024 subcarriers). Pilots are situated in SBs (see Figure 11.3, right). Each terminal is identified by an orthogonal sequence along the frequency axes. Time and frequency interpolation are separately performed. In the time domain interpolation, possible amplitude differences inside a resource unit have been ignored. The mean phase drift is evaluated for each terminal inside the rectangle indicated in. Pilots available on identical subcarriers in the two SBs are used for estimation of . To reduce noise, raw estimates H are averaged as (11.2) Frequency domain interpolation in uplink exploits the fact that the coefficient measured at a given pilot carrier i in an SB corresponds to the carrier with index 2 X i in an LB. The odd number of 25 carriers causes overlap at the edges of resource units (see Figure 11.3, right). We have performed local interpolation over two adja- cent resource units, accordingly. While the channel estimates are used to compute weight matrices for multiuser detection, the phase values are passed to a phase tracking unit placed after the multiuser detector operating a