uplink subframe. A combined TDM/FDM and TDM/CDM scheme is used to 10.3 Uplink control channels multiplex multiple HARQ feedback channels. It was mentioned earlier that each HMT is identified by two indices: m is the HMT index in a HARQ feedback channel where m takes values 0, 1 or 2; and k is the HARQ feedback channel index where k takes an integer value in the range 0 to LHFB-FPi - 1. The HARQ feedback channel comprises three distributed uplink feedback mini-tiles where the uplink FMT, as defined earlier, consists of two sub-carriers over six OFDM symbols. A total of three distributed 2 X 6 UL FMTs can support six UL HARQ feedback channels. The 2 X 6 UL FMTs are further divided into UL HARQ mini-tiles. An uplink HARQ mini-tile is constructed by two sub- carriers over two OFDM symbols, as illustrated in Figure 10-14. The uplink HARQ feedback channels are physically processed as follows. Each pair of HARQ feedback channels (i.e., a pair of one-bit uplink HARQ feedback channels with even- and odd-valued indices) are mapped to a pair of orthogonal 4-bit sequences (Cio Cil Ci2 Ci3, i = 0,1,2,3 shown in Table 10- 19), depending on whether their corresponding index is odd or even. The resulting orthogonal sequences occupy one HMT which is repeated three times over three HMTs, as shown in Figure 10-14. In other words, each pair of uplink HARQ feedback channels is code-division multiplexed over one HMT and then repeated three times over three pairs of OFDM symbols to achieve time and frequency diversity. It can be seen that each group of three reordered FMTs can support up to six single-bit HARQ feedback channels. At the receiver, even- and odd-indexed HARQ feedback channels are decoded by the inner product of the orthogonal sequences shown in Table 10-19, and the received content of the uplink HARQ feedback channel. Since the HARQ feedback channels are sequentially indexed, there will be one even and one odd index in each pair whose corresponding sequences are orthogonal. HARQ Feedback Channels i and j HARQ Mini-Tile UL