Gain of 64QAM in Macrocellular HSPA+

The current (11/2009) de-facto mobile broadband configuration in commercial HSDPA networks is the 7.2 Mbps defined in 3GPP Release 5. During the second half of year 2009 a lot has happened in HSPA; new terminals with 15-code support (Category 9 and Category 10) have been introduced and further development is expected to happen in 2010. Release 7 HSPA+ features are becoming available in practical networks introducing increased performance of mobile broadband services.

In this paper we investigate the gains of increasing the maximum modulation order from 16QAM to 64QAM in macro-cellular HSPA networks with 15 HS-PDSCH codes. 64QAM is a Release 7 feature increasing the peak air interface bitrate to 21.6 Mbps with Category 14 terminals. The most advanced Release 6 terminal, that is Category 10, only supports 16QAM and air-interface bitrate of 14.4 Mbps. These figures, which are often used for marketing purposes, thus suggest a 50% improvement to be available. From telecom operator perspective it seems very feasible as the feature itself is generally a simple software upgrade to the network and the terminals are soon widely available.

As the peak bitrate is a poor KPI for evaluating the performance of technologies in general, we approach the issue with a more detailed study. The performance gain is assessed with theoretical background study, real life measurements and system simulations.

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