An Uplink Multiple Access Scheme Using Pilot-Free Channel Estimation

In an uplink scenario, a base station can extract messages from multiple users through received symbols according to individual channel gains. There is a multiple access scheme relying on channel gains for separating users which is referred to as gain division multiple access (GDMA). Our goal is to provide channel estimation for the GDMA system without using pilot signals. We first employ a clustering technique to obtain estimates of the possible linear combinations of channel gains of users through a set of received symbols. We then devise algorithms to estimate the channel gain for each user and recover the message sent from each user.