1. R99 is the original standard for UMTS WCDMA based networks. HSDPA is an add on to
R99/UMTS networks which adds a shared high speed downlink packet channel. There is a
partner to HSDPA for the uplink known as HSUPA (High Speed Up Link Packet Access) or EUL
(Enhanced Uplink) as well which can boost uplink speeds to at least 1.9Mbit/s and I believe
higher (but I cant recall the highest speed it can do – I think it is 7.2Mbit/s).
R99 supports CS Voice/Video and PS up to 384Kbit/s DL/UL. HSDPA with Class 10 devices
can support on a shared channel up to 14.4Mbit/s.
HSPA Data Rates Calculation
People often get lost while calculating the data rates for HSDPA, HSUPA or HSPA+
Note: HSPA+ is better known as eHSPA or HSPAe where e stands for evolution or evolved
Most people are aware that the theoretical maximum for HSDPA is 14.4Mbps, so lets see how we reach
14.4Mbps:
In UMTS, in each slot the maximum number of bits transmitted is 2560. The correct term to use is chips rather than bits.
If you want to know where this 2560 comes from or why chips then please refer 3GPP TS 25.211
There are 15 slots per 10ms frame so since the TTI for HSDPA is 2ms, there will be 3 slots. So there will be a total of 7680
chips.
QPSK has 2 bits per symbol = 7680 * 2 chips for 2ms = 15360 chips/2ms = 15360 * 1000 /2 chips per second
Now the SF is fixed at 16
= (15360 * 1000) / (2 * 16)
= 480 Kbps
Terminal that uses 15 QPSK codes will get 480 * 15 = 7.2Mbps
On other hand 16 QAM will have 4 bits per symbol so the rate would be 7.2 * 2 = 14.4Mbps
In HSPA+ we will also have 64QAM which has 6 bits per symbol (2^6 = 64) so the max rate would be 7.2 * 3 = 21.6Mbps.
