In SOMA, additional uplink data after each pilot symbol is transmitted. Uplink channel estimation and decoding of users is done in a sequential manner, through sequential channel estimation with successive interference cancellation. Pilot symbols of the first user are transmitted orthogonally to both pilot and data symbols of all other users and any other users data is nonorthogonally, that is, concurrently transmitted with only one
user’s pilot symbols (“semiorthogonal” is used to describe this feature). We can also
add new users because we do not need to sacrifice the uplink data transmission of the