Operation of portable HF CDMA networks with controlled transmitter powers

The use of networks consisting of portable HF radios multiplexed to a master station requires an effective supervision system. Spread-spectrum code-division multiple access provides flexibility in the number of users and has advantages over time and frequency multiple-access techniques for this type of network in that precise time or frequency co-ordination between the users is not needed. However, possible near-far problems due to other-user interference and the desire to reduce the peak power in order to reduce the detectability to nonmembers of the network make it necessary to enforce control of the transmitter powers. It is shown that when the transmitter powers are well controlled the added power required to combat the other-user interference is small for a wide range of network users. As the control gets less accurate or no control is applied, the added power required owing to multiplex operation becomes larger, and ultimately no increase in power will save the network from degrading. The controlled transmitter power scheme is applied both to networks of ground-wave links and to networks of sky-wave links. For the ground-wave links it may be assumed that a propagation parameter is represented by one number, as compared with sky-wave links, where the parameters are time varying and are best described by statistical distributions.