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Near-Optimal Reduced-Complexity Sequence Detectors for TD-HSPA

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A tree portion of the progressive grouping stage with MLD pruning, which is used in the pre-processing step in a low-complexity sequence detector.




Karim Badawi


Hasler Foundation




TD-HSPA is a standard that emerged from China initially known as TD-SCDMA, which was later adopted by 3GPP. It uses a TDMA channel access method combined with an adaptive synchronous CDMA component on 1.6 MHz slices of spectrum, allowing deployment in even tighter frequency bands than TD-CDMA.

It exhibits a flexible TDD asymmetric nature giving it an advantage over other 3G standards, and providing a flexible data rate upto 2.8Mbit/s.

TD-HSPA operates over physical channels in multipath propagation conditions, hence, severe inter-symbol interference is experienced by the User Equipment (UE) at high mobility speeds upto 120 km/h.

In order to bring this to practice, clever multiuser detection and equalization techniques have to be deployed at the UE. However, this task is not a trivial one in an environment such as that of the TD-HSPA standard (deploying higher order modulation up-to 64-QAM and multiplexing of up-to 16 CDMA codes).

In this project, novel and well-known techniques such as Zero-Forcing equalizer, MMSE linear equalizer, MMSE-SIC, and MMSE-PIC detectors have been implemented and investigated with focus on their performance/complexity tradeoff. Additionally, a novel guided (non-exhaustive) sequence detection algorithm has been designed and investigated, and its performance was found to approach that of the ideal exhaustive search algorithms..