1. In UMTS, various OVSF codes with different spreading factors are generated by doubling a chipping sequence with and without flipping the sign of the chips.

• State the condition under which two OVSF codes are orthogonal.
• Three sets of different OVSF codes are given below, and just one set can support simultaneous transmissions of signals. State which OVSF code set is valid.

1. (1, -1), (1,-1,1,-1) and (1,1,1,1,1,1,1,1)
2. (1), (1,-1) and (1,1,1,1,1,1,1,1)
3. (1,-1), (1,1,-1,-1) and (1,1,1,1,1,1,1,1)

• Assuming the fixed chipping rate is fixed, for the valid OVSF code set identified above, if a signal data rate of 1Mb/s is supported by the OVSF code with the largest spread factor, work out the signal bit rates supported by other two OVSF codes.State whether or not the use of the OVSF chipping sequences with different spreading factors affects the signal bandwidths.
• Assuming the chipping rate is proportional to spreading factor, work out the maximum/minimum received bit values associated with each of the valid OVSF codes.