WCDMA Uplink Parallel Interference Cancellation—System Simulations and Prototype Field Trials

Abstract

Interference cancellation (IC) is one identified key technology to enhance WCDMA uplink performance. The goal of this contribution is to highlight the relative uplink system capacity improvement available for WCDMA, especially in realistic typical urban radio environments when employing receiver implementations including realistic channel estimation, searcher, and so forth. The performance of the selected limited-complexity parallel IC receiver is first evaluated with link-level simulations in order to provide input to system-level simulations. The system-level methodology is explained and a 40% system-level uplink capacity increase compared to utilizing the conventional RAKE receiver is found. The limited-complexity parallel IC receiver is then evaluated in a single-cell field trial. The trials show that both the mean and the variance of the outer-loop power control is reduced, which implies an overall increased capacity and an increased battery life of the terminals. Furthermore, the observed capacity gains are in accordance with system simulations.

Adaptive Duplicated Filters and Interference Canceller for DS-CDMA Systems

“…8: (1) the effective code computation, b Θ k t; n ð Þ, for all K users, (2) the synthetic signal construction using (13) and (3) the coefficients' update using an adaptive method based on SM-NLMS [29], to return w k (16)- (18). Figure 8 presents the timing diagram for these operations.…”

“…The coefficients' adaptation is divided in three other sub-operations each as a PE (Fig. 9): (1) the adaptation filter block (FB adapt ) to compute the equations (6)- (8), (2) (16) and (18), and (3) the update block (UB) for (17). Each of operators is executed by respective PE which have particular characteristics: Fig.…”

“…In comparison to the conventional Rake receiver, Hagerman and al. showed in [18] the uplink capacity improvement for WCDMA when using a MPIC: a 40% system-level increase has been found in typical urban environment for a voice transmission (12.2 kbps). Authors estimated that this MUD is 5 times more complex than Rake receiver, doubling the total receiver complexity.…”

“…Unfortunately, this optimal MUD is prohibitively complex for real-time implementation; its complexity increases exponentially with the number of users. Therefore, over the last two decades, research in this area has focused on several uplink sub-optimal MUD solutions [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] whose design objective is to reach a good tradeoff between performance and complexity: (1) to combat MAI and ISI in order to reliably detect information data of possibly a larger number of active users; while (2) maintaining a complexity permitting a real-time implementation for this maximum number of users. This implementation complexity issue explains the reason why the Rake receiver is still present in 3G base stations [4].…”

“…These IC MUD methods based on autocorrelation codes matrix shows excellent performances in combating MAI at the expense of a huge complexity. For acceptable complexity level most works do not use autocorrelation matrix [4] wherein works on their VLSI implementation appears in [17][18][19][20][21][22]. In comparison to the conventional Rake receiver, Hagerman and al.…”