A base station subsystem, BSS, configured to interact with a plurality of mobile stations (104 1, 104 2, 104 3, 104 4....104 n) and perform a procedure to improve an Access Grant Channel, AGCH, capacity, the BSS comprising: a processor; and a memory that stores processor-executable instructions where the processor interfaces with the memory and executes the processor-executable instructions to enable the following operations: broadcast a new system information, SI, to the plurality of mobile stations, where the new SI includes static radio parameters which are to be used by any one of the plurality of mobile stations when establishing an uplink Temporary Block Flow, TBF, to transmit a small data transmission, SDT, or an instant message transmission, IMT; receive, during an access time interval, multiple access requests from multiple mobile stations (104 1 and 104 3) of the plurality of mobile stations, where the multiple mobile stations are each requesting to establish their respective uplink TBF to transmit the SDT or the IMT; and in response to the received multiple access requests, send an immediate assignment message on the AGCH addressed to the multiple mobile stations, where the immediate assignment message includes multiple instances of at least a portion of dynamic radio parameters, wherein each one of the multiple mobile stations are to use their respective instance of the at least a portion of dynamic radio parameters along with the static radio parameters when establishing their respective uplink TBF to transmit the SDT or the IMT, and wherein the immediate assignment message has a constant format and a constant number of octets when addressing a variable number of the multiple mobile stations. a processor; and a memory that stores processor-executable instructions where the processor interfaces with the memory and executes the processor-executable instructions to enable the following operations: broadcast a new system information, SI, to the plurality of mobile stations, where the new SI includes static radio parameters which are to be used by any one of the plurality of mobile stations when establishing an uplink Temporary Block Flow, TBF, to transmit a small data transmission, SDT, or an instant message transmission, IMT; receive, during an access time interval, multiple access requests from multiple mobile stations (104 1 and 104 3) of the plurality of mobile stations, where the multiple mobile stations are each requesting to establish their respective uplink TBF to transmit the SDT or the IMT; and in response to the received multiple access requests, send an immediate assignment message on the AGCH addressed to the multiple mobile stations, where the immediate assignment message includes multiple instances of at least a portion of dynamic radio parameters, wherein each one of the multiple mobile stations are to use their respective instance of the at least a portion of dynamic radio parameters along with the static radio parameters when establishing their respective uplink TBF to transmit the SDT or the IMT, and wherein the immediate assignment message has a constant format and a constant number of octets when addressing a variable number of the multiple mobile stations. broadcast a new system information, SI, to the plurality of mobile stations, where the new SI includes static radio parameters which are to be used by any one of the plurality of mobile stations when establishing an uplink Temporary Block Flow, TBF, to transmit a small data transmission, SDT, or an instant message transmission, IMT; receive, during an access time interval, multiple access requests from multiple mobile stations (104 1 and 104 3) of the plurality of mobile stations, where the multiple mobile stations are each requesting to establish their respective uplink TBF to transmit the SDT or the IMT; and in response to the received multiple access requests, send an immediate assignment message on the AGCH addressed to the multiple mobile stations, where the immediate assignment message includes multiple instances of at least a portion of dynamic radio parameters, wherein each one of the multiple mobile stations are to use their respective instance of the at least a portion of dynamic radio parameters along with the static radio parameters when establishing their respective uplink TBF to transmit the SDT or the IMT, and wherein the immediate assignment message has a constant format and a constant number of octets when addressing a variable number of the multiple mobile stations.