Definition: PSIST() is a parameter used to randomize the times between access probe sequences when the mobile is making an autonomous access channel request.
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Example: PSIST(N), N decimal zero to 9 is a 6-bit word and for N from 10 to 15 inclusive PSIST(N) is a 3-bit word. The value of N is referred to as the access overload class. If the system gets into an overload condition, PSIST() can be used to determine which mobiles are allowed to access the system. The persistence value, P, calculated using PSIST() is essentially the probability that any one of the persistence trials or tests will be successful, which then allows the mobile to transmit. For instance, P when the access channel request is other than a registration or a message transmission is given by the equations P = 2-PSIST(N)/4 if PSIST(N) ≠ 63 and is zero otherwise (1) when N equals decimal 0, 1, 2, ..., 9. When N equals 10, 11, ..., 15, P equals P = 2-PSIST(N) if PSIST(N) ≠ 7 and is zero otherwise (2) For example, suppose PSIST(6), the PSIST value for overload class 6, equals decimal 8. The 6-bit binary word allocated to PSIST(6) equals 001000. In the message case covered by Eq. (1) above, the probability that a given trial will result in a self-calculated right to transmit is P equal to 2-2 or 1/4. If PSIST(6) equals binary 111111, or decimal 63, P equals zero. In this case, the mobile assigned to overload class 6 is not allowed to access the system. The value of P is expected to be small enough that 1/P equals or is a small integer factor greater than the number of mobiles per access channel trying to access the system. USE YOUR BROWSER "BACK" BUTTON TO RETURN © 1999 DR. ERNEST SIMO - SPACE2000 |
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