Pilot design and channel estimation for uplink block spread CDMA

In this paper, we propose the pilot design and channel estimation schemes for uplink block-spread code division multiple access (BS-CDMA) systems. In particular, we propose the use of a common spreading code to spread the pilot signals of all users such that a high bandwidth efficiency is achieved. The expense, however, is the multi-user interference (MUI) introduced in uplink channel estimation. On that account, three pilot design schemes are proposed to eliminate the MUI. We show through simulations that, a BS-CDMA system using the proposed pilot design schemes with recursive least squares (RLS) channel tracking algorithm achieves a comparable performance to a similar system using the pilot block based channel estimation (as employed in the LTE uplink) in low mobility scenario, while significantly outperforming that using the pilot block based channel estimation in high mobility scenario. In particular, the performance of BS-CDMA using the proposed channel estimation methods remains robust at a Doppler frequency of 400Hz.