Tuesday, February 15, 2011

Higher Order Modulation (HOM)

HSPA supports 16QAM modulation on the downlink and QPSK on the
uplink. As Figure 4 shows, the data capacity (bits/symbol) increases as
we move from QPSK to 16QAM and 64QAM. HSPA+ R7 introduces
64QAM on the downlink, which increases the data rates by 50% for
devices in good signal conditions (high SNR). On the uplink, 16QAM
doubles data rates for devices that are not power headroom limited.

Wireless signals transmitted with a higher modulation are more sensitive
to interference and require a higher SNR at the receiver for successful
demodulation. HOM significantly increases the data rates for users with
high SNR. Hence, the traffic for these users can be serviced faster,
leaving Node B with more time and resources to service users in weaker
signal areas, such as the cell edge. Overall, this provides high data rates
and improved user experience for all users in the cell.


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