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A Novel Constrained-Viterbi Algorithm with Linear Equalization and Grouping Assistance

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Top: A block diagram of the LEG-CVA receiver. Bottom: Modem Bit-Error-Rate vs. Received Signal-to-Noise Power Ratio for TD-HSPA, Case-3 Multipath Channel, 16-CDMA codes and 64-QAM.




Karim Badawi
Christian Benkeser
Christoph Roth


Hasler Foundation




Modern wireless communication standards have witnessed a rise in throughput requirements. This has reflected onto the design of multiple access (MA) schemes, where recent standards incorporate several MA techniques simultaneously.

Moreover, higher order modulation techniques such as 16- and 64-QAM are utilized. Consequently, such systems have relatively large dimensions. When the channel is time-dispersive, inter-symbol interference (ISI) and the inherent multiple-access interference (MAI) become challenging problems to resolve in order to meet the standards’ premise of high throughput.

In this project, we devised a novel linear equalization and progressive grouping-assisted constrained Viterbi algorithm (LEG-CVA) as a near-maximum likelihood sequence estimation (MLSE) approach for the downlink.

The published results show that the reduced-complexity algorithm is highly attractive with large system dimensions such as those in the time-duplexing high speed packet access (TD-HSPA) system.

The new two-step algorithm performs better than traditional sub-optimal equalizers with a much lower complexity than traditional joint detection schemes. LEG-CVA can be used in many scenarios such as DS-CDMA or multiple-input multiple-output (MIMO) reception.


  • K. Badawi, C. Benkeser, C. Roth, Q. Huang, A. Burg, "A Novel Constrained-Viterbi Algorithm with Linear Equalization and Grouping Assistance", IEEE International Symposium on Wireless Communication Systems (ISWCS), Paris, France, 28 Aug 2012