This paper, originally distributed as ARPA Satellite System Note 8 in 1972, explores methods to enhance the effective channel capacity of ALOHA packet systems, particularly for satellite and ground radio channels. The author, Lawrence G. Roberts, discusses two main approaches: using slots and leveraging capture effects. 1. **Slot Systems**: Roberts proposes dividing the channel into time slots, where devices must start transmitting packets at the beginning of each slot. This method can significantly improve channel capacity, especially for satellite channels, where it can double the capacity. 2. **Capture Effects**: The paper examines how receivers can "capture" stronger signals from collisions, allowing for the correct reception of one of the conflicting packets if one signal is significantly stronger. This is particularly useful in FM receivers, where the capture ratio (the difference in signal strength between the strongest and second-strongest signals) plays a crucial role. The paper also provides detailed mathematical derivations to analyze the performance of these systems, including the probability of successful packet reception, the average bit rate, and the delay encountered by packets. It concludes that slot systems can improve capacity by up to 60% for ground radio channels, while capture effects can further enhance performance, especially in FM receivers. The choice between slot systems and asynchronous systems depends on the specific channel conditions and the required delay.This paper, originally distributed as ARPA Satellite System Note 8 in 1972, explores methods to enhance the effective channel capacity of ALOHA packet systems, particularly for satellite and ground radio channels. The author, Lawrence G. Roberts, discusses two main approaches: using slots and leveraging capture effects. 1. **Slot Systems**: Roberts proposes dividing the channel into time slots, where devices must start transmitting packets at the beginning of each slot. This method can significantly improve channel capacity, especially for satellite channels, where it can double the capacity. 2. **Capture Effects**: The paper examines how receivers can "capture" stronger signals from collisions, allowing for the correct reception of one of the conflicting packets if one signal is significantly stronger. This is particularly useful in FM receivers, where the capture ratio (the difference in signal strength between the strongest and second-strongest signals) plays a crucial role. The paper also provides detailed mathematical derivations to analyze the performance of these systems, including the probability of successful packet reception, the average bit rate, and the delay encountered by packets. It concludes that slot systems can improve capacity by up to 60% for ground radio channels, while capture effects can further enhance performance, especially in FM receivers. The choice between slot systems and asynchronous systems depends on the specific channel conditions and the required delay.