(a) Refer to the differential encoder used in Figure a. Table 6.10 defines the phase changes induced in the V.32 modem by varying input debits. Expand this table by including the corresponding previous and current values of the differential encoder’s output. Note that for every input debit there are four possible values for the differentially encoded debit and likewise for its previous value I1,n-1 I2,n-1.
(b) The current quad bit applied to the V.32 modem with non-redundant coding is 0001. The previous output of the modern is 01. Find the code word output produced by the modem and its coordinates.