Just when we thought that we have squeezed every bit out of HSPA, a surprise waiting is the speeds of upto 168Mbps in the downlink. Going back to the 3G Americas report, there is a section in the end that details HSPA+ enhancements for Rel-10:
Rel-8 introduced dual-carrier HSDPA operation in the downlink while Rel-9 similarly introduced dual-carrier HSUPA operation in the uplink and also enhanced the dual-carrier HSDPA operation by combining it with MIMO.
Further enhanced multi-carrier HSDPA operation is being specified for Rel-10, where the base station will be able to schedule HSDPA transmissions over three or four carriers simultaneously to a single user with the carriers are spread over one or two frequency bands. Solutions specified in earlier releases can be reused to a large extent. The difference is that now it is possible to configure a UE with one primary serving cell and up to three secondary serving cells. As in earlier releases, the secondary serving cells can be activated and deactivated dynamically by the base station using so-called “HS-SCCH orders.” With MIMO transmission on all four carriers, the peak rate would be doubled to 168 Mbps compared to Rel-9 and for typical bursty traffic the average user throughput would also experience a substantial increase.
Remember, I posted a blog on data rates calculation? The maximum data rate in Release-8 HSDPA is 42Mbps. With Dual-carrier operation, this could be doubled to 84Mbps. As you can probably guess, with 4 carriers, this will become 168Mbps ;)
For people who are less technically inclined, can check this Ericsson presentation on HSPA+ data rates. For people who may become sleepless without some technical references can check this report from RAN WG#1 meeting#59. If you are not sure what RAN WG#1 is, check quick tutorial on 3GPP here.
Going back to the 3GPP report, section 5.4 lists the details of 4 carriers HSDPA. It would be interesting to see what happens in cases where initially there were 4 carriers but then in a particular spot it changed to 2 carriers, and vice-versa. People who have yet to work on LTE may not have to worry too much as HSPA is being future proofed against the threats of LTE and WiMAX.
Interestingly enough, HSPA+ offers a better and cleaner solution at the moment especially with regards to voice calls and handing over to GSM then LTE or WiMAX.
It wont come as a surprise if the HSPA+ camp are able to pull out some new tricks from their bag just in time for Release-11.