selection in hardware. (d) Efficient use of memory in the receiver. Thus, these sequences have potential applications in both the multiple access and jamming environments. Table 5.19 Properties of sequence sets with period 2d - 1. maximum maximum achievable achievable linear Family linear span span for d < 20 2d + 1 1 + 2(d+1)/2 (mod 4) 2d + 1 1 + 2(d+2)/2 Kasami (small set) 1 + 2dl2 Kasami (large set) 2dr2(2d + 1) 1 + 2(d+2)/2 Sequences 0 (mod 4) 1 + 2d12 (d/2)2414 Pseudonoise Generators 5.8 FREQUENCY-HOPPING MULTIPLE-ACCESS DESIGNS 5.8.1 Design Criteria The design of PN sequences to be used in frequency-hopping multiple-access (FHMA) systems differs from DSMA design in several ways: 1. The sequences' alphabet size is larger in an FHMA design, with one alphabetical character for each synthesizable frequency. In the DSMA case, that alphabet size usually corresponds to the number of carrier phase shifts used to modulate the sequence, the number typically being two (BPSK) or four (QPSK). Interference occurs in a FHMA system when two distinct transmitters use the same frequency simultaneously. Hence, the Hamming distance between the FH sequences being used by the transmitters is a measure of the quality of the sequence design, the ideal design possessing the maximum possible distance between FH sequences. In the DSMA case, optimal designs were based on minimum absolute corelation between sequences, which corresponded, in the binary case under ideal condi- tions, to a design in which all Hamming distances between sequences were equal to half the number of symbols over which the distances were being calculated. 3. The one-to-one mapping of a PN generator's output symbols into fre- quencies in a FHMA system is arbitrary and preserves Hamming dis- tance. If this mapping can be changed by the system operators, e.g., used as a code-of-the-day, this may make the system less susceptible to jam- mers attempting to predict the hopping pattern, but should not be relied upon, as a substitute for large linear span, to baffle int