The vulnerable period of slotted ALOHA is _ packet duration.Ĭlarification: The vulnerable period of slotted ALOHA is one packet duration. After a transmission, the user waits for an acknowledgement on either the same channel or a separate feedback channel.ġ0. For pure ALOHA protocol, the vulnerable period is _ the packet duration.Ĭlarification: For the pure ALOHA protocol, the vulnerable period is double the packet duration. A user accesses a channel as soon as a message is ready to be transmitted.ĩ. The unit of R is in Erlangs.Ĭlarification: The pure ALOHA protocol is a random access protocol used for data transfer. If λ is mean arrival rate and τ is the packet duration, then traffic occupancy of a packet radio network is equal to _Ĭlarification: If λ is mean arrival rate and τ is the packet duration, then traffic occupancy or throughput of a packet radio network is equal to λτ. To study packet radio protocols, it is assumed that all packets sent by all users have a constant packet length and fixed channel rate.ħ. For a PR multiple access technique, packet transmissions occur with _ distribution.Ĭlarification: For a PR multiple access technique, packet transmissions occur with Poisson distribution. It is used in order to determine the throughput.Ħ. What is the time period during which the packets are susceptible to collisions with transmissions from other users?Ĭlarification: Vulnerable period is the time period during which the packets are susceptible to collisions with transmissions from other users. _ is defined as average number of messages successfully transmitted per unit time in packet radio multiple access technique.Ĭlarification: The performance of contention technique can be evaluated by the throughput (T), which is defined as the average number of messages successfully transmitted per unit time, and the average delay experienced by a typical message burst.ĥ. The subscriber uses a contention technique to transmit on a common channel.Ĥ. Packet radio has high spectral efficiency.Ĭlarification: Packet radio multiple access is very easy to implement, but has low spectral efficiency and may induce delays.
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The ACK signal indicates an acknowledgment of a received burst and NACK indicates that the previous burst was not received correctly by base station.ģ.
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Packet radio uses _ and _ signals for perfect feedback.Ĭlarification: Packet radio uses ACK and NACK signals for perfect feedback. Transmission is done by using bursts of data.Ģ. In _ technique, many subscribers attempt to access a single channel in an uncoordinated manner.Ĭlarification: In packet radio (PR) access techniques, many subscribers attempt to access a single channel in an uncoordinated (or minimally coordinated) manner. Wireless & Mobile Communications Multiple Choice Questions on “Packet Radio”.ġ.