LTE and HSPA Uplink Power Control in Comparison

And here's my LTE thought of the day:

One of the fascinating things about the 3G/WCDMA/HSPA uplink is the 1500 power control commands per second to ensure all devices transmitting at the same time are received with a similar power level. This is necessary as only this way the base stations can retrieve the individual data streams that are stacked on each other in the code/power domain. 

With LTE, however, such a fast power control is no longer required as each mobile sends at a different time or uses different subcarriers (i.e. different time / frequency domains). While it is still necessary that all transmitting devices are received by the base station with "more or less" the same power in order not to overload the A/D converters it is by no means as essential as before. A lot less work and signaling involved that way.

Comments

[Topper Harley]

It's 1500 times per second, isn't it?

[Martin]

yup, 1500 it is. Duly corrected sir, thank you! :-)

Kind regards,
Martin

[David Boettger]

Incidentally, TD-SCDMA (UMTS-TDD LCR) utilizes orthogonal code division within timeslots on the uplink which reduces somewhat the need for fast uplink power control.

Of course, in both LTE and TD-SCDMA, maintaining orthogonality on the uplink is dependent on good time synchronization amongst uplink transmissions from different users. Dispensing with fast power control has its cost.