HSDPA Terminal Capability and Achievable Data Rates

yaziz  Diamond  (1)
6 years 5 months ago  View: 4867  Reply: 30

The HSDPA feature is optional for terminals in Release 5 with a total of 12 different categories of terminal (from a physical layer point of view) with resulting maximum data rates ranging between 0.9 and 14.4 Mbps. The HSDPA capability is otherwise independent from Release ’99-based capabilities, but if HS-DSCH has been configured for the terminal, then DCH capability in the downlink is limited to the value given by the terminal. A terminal can indicate 32, 64, 128 or 384 kbps DCH capability. The first ten HSDPA terminal capability categories need to support 16 QAM, but the last two, categories 11 and 12, support only QPSK modulation. The differences between classes lie in the maximum number of parallel codes that must be supported and whether the reception in every 2 ms TTI is required. The highest HSDPA class supports 10 Mbps. Besides there is the soft buffer capability with two principles used for determining the value for soft buffer capability. The specifications indicate the absolute values, which should be understood in the way that a higher value means support for incremental redundancy at maximum data rate, while a lower value permits only soft combining at full rate. While determining when incremental redundancy can be applied also, one needs to observe the memory partitioning per ARQ process defined by the SRNC. There is a maximum of eight ARQ processes per terminal.

Category number 10 is intended to allow the theoretical maximum data rate of 14.4 Mbps, permitting basically the data rate that is achievable with rate 1/3 turbo coding and significant puncturing, resulting in the code rate close to 1. For category 9, the maximum turboencoding block size (from Release ’99) has been taken into account when calculating the values, thus resulting in the 10.2 Mbps peak user data rate value with four turbo-encoding blocks. It should be noted that, for HSDPA operation, the terminal will not report individual values but only the category. The classes shown are as included in with 12 distinct terminal classes. From a Layer 2/3 point of view, the important terminal capability parameter to note is the RLC reordering buffer size that basically determines the window length of the packets that can be ‘in the pipeline’ to ensure in-sequence delivery of data to higher layers in the terminal. The minimum values range from 50 to 150 kB, depending on the UE category.

Besides the parameter part of the UE capability, the terminal data rate can be largely varied by changing the coding rate as well. Table shows the achievable data rates when keeping the number of codes constant and changing the coding rate as well as the modulation. Table shows some example bit rates without overhead considerations for different transport format and resource combinations (TFRCs).

These theoretical data rates can be allocated for a single user or divided between several users. This way, the network can match the allocated power/code resources to the terminal capabilities and data requirements of the active terminals. In contrast to Release ’99 operation, it is worth noting that the data rate negotiated with the core network is typically smaller than the peak data rate used in the air interface. Thus, even if the maximum data rate negotiated with the core network was, e.g., 1 Mbps or 2 Mbps, the physical layer would use (if conditions permit) a peak data rate of, e.g., 3.6 Mbps.

shahiduzzaman  Medium 
6 years 5 months ago
very good article.
suman.s  Medium 
6 years 5 months ago
its an interesting post.
sajid123  Medium 
6 years 5 months ago
very cool post
tkhan  Medium 
6 years 5 months ago
nice information
rohidul  Medium 
6 years 5 months ago
it is an interesting post. thanks.
shekhar123  Medium 
6 years 5 months ago
this is very excellent post. 
s_khaleque  Medium 
6 years 5 months ago
thanks for the information.
rukunuzzaman  Medium 
6 years 5 months ago
thanks for sharing
zamshed.ali  Medium 
6 years 5 months ago
very useful info. need more detail.