Iterative MMSE equalization and CFO compensation for the uplink SC‐FDMA transmission

Abstract

SUMMARYSingle-carrier frequency division multiple access is greatly sensitive to carrier frequency offset (CFO) between transceivers. This leads to the destruction of orthogonality among subcarriers, which in turn leads to intercarrier interference and multiple access interference between different users. Minimum mean square error (MMSE) equalizer that uses an inverse operation on an interference matrix with a dimension equal to the number of subcarriers is normally used to invalidate CFO effects. Hence, the terminal processing complexity is very high. The proposed conjugate gradient method attempts to mitigate the higher computational complexity by iteratively evaluating the MMSE solution without direct matrix inverse operation. To further mitigate the multiple access interference, MMSE combined with parallel interference cancellation is also implemented. The analysis of the proposed method shows better performance and fast convergence in single-carrier frequency division multiple access systems. The maximum iteration number to formulate an accurate solution is almost equal to the number of active users in the uplink access. Simulation results bring out the effectiveness of the present method compared with the existing CFO compensation schemes in terms of computational complication and system performance with large frequency offsets.

BER analysis and interference mitigation for GO‐OFDMA transmission

“…In the similar manner, as shown for variable rate scenario, using (4) to (7) and (A2), the detected bit for single rate scenario can be produced and shown in a manner as shown in (9).…”

“…Effect of CFO in different schemes had been investigated in previous literature. [2][3][4][5][6][7][8] One way is to use multiuser detection (MUD). But MUD is relatively complex that imposes computational as well as power burden on the receiver and its complexity increases with the number of users.…”

Low complexity ordered successive interference cancelation detection algorithm for uplink MIMO SC‐FDMA system

“…Maximum likelihood (ML), minimum mean square error (MMSE), and zero forcing (ZF) receivers are exploited to detect the transmitted data for MIMO SC-FDMA systems [5][6][7][8]. ML detection offers the best bit error rate (BER) performance where detection difficulty increases exponentially, particularly with the increase in data streams, user equipment, and antennas.…”

Carrier frequency offsets problem in recent DST‐SC‐FDMA system: Investigation and compensation

“…CFOs problem in multicarrier systems was extensively studied in the literature [10][11][12]. Feedback and compensation approaches have been proposed to reduce and mitigate the impacts of CFO when used for uplink transmission [13][14][15]. In our previous work [16], the impacts of CFO on SC-FDMA performance was investigated and analyzed with consideration of different subcarriers mapping schemes where the localized subcarrier mapping (LFDMA) and interleaved subcarrier mapping (IFDMA) schemes are used.…”