Evaluation of HSDPA and LTE by Sebastian Caban & Christian Mehlfuhrer & Markus Rupp & Martin Wrulich

Author:Sebastian Caban & Christian Mehlfuhrer & Markus Rupp & Martin Wrulich
Language: eng
Format: epub
Publisher: Wiley
Published: 2011-09-28T16:00:00+00:00

In order to compensate for the above effects, one would have to apply a much better channel estimator for MIMO than in the case of SISO transmissions.

Figure 8.4 SNR losses of different channel estimators and channel coding schemes with respect to genie-driven channel estimation and LDPC coding; measured in the alpine scenario.

Figure 8.5 Throughput and bounds of HSDPA 1 × 1 and 2 × 2 transmissions: left, alpine; right, urban; top, SISO; bottom, MIMO.

8.4.2 HSDPA Results in Standard-Compliant Setting

All measurement results presented in this section are for a Category 16 HSDPA user equipment. In the MIMO case, a Double Transmit Antenna Array (D-TxAA) with adaptive precoding is applied [4].

The various losses of HSDPA as depicted in Figure 8.5 (absolute values) and Figure 8.6 (relative losses) show a much less lively picture when compared with WiMAX.

Relative CSI loss: As before, this decreases monotonically in exactly the same dimensions as the CSI loss is independent of the transmission standard, proving that both measurements have experienced the same equipment as well as the same wireless conditions. Small differences when compared with the WiMAX results are due to a slightly different occupied bandwidth.

Relative design loss: The other losses are more or less constant functions or slightly increasing with PTx. The relative design loss with values between 30 and 40 % is a particularly flat curve when compared with WiMAX. Only at low PTx in the urban MIMO scenario can the values become as small as 15 %.

Relative implementation loss: This is either of the same value as the design loss or larger. The distinct behavior in the urban scenario is of interest. Owing to the larger RMS delay spread in the urban scenario, the inter-code interference is increased and becomes a dominant part at high PTx. Therefore, we recognize a higher implementation loss and a smaller design loss for high PTx.

Absolute implementation loss: This behaves very differently for WiMAX and HSDPA, as can be observed in Figure 8.5. In environments with large RMS delay spread (urban environment with 1.1 μs) the implementation loss of HSDPA is extremely large due to self-interference while in small RMS delay spread areas (alpine environment with 260 ns) the behavior is different.

Relative throughput: Similar to WiMAX, this is an increasing function in SNR. For low values of PTx the spreading functions of HSDPA improve the situation considerably, allowing a transmission even for very low receiver SNR at low bit rates. Furthermore, HSDPA has many more AMC schemes than WiMAX, especially at low SNR. At high PTx we obtain in the alpine environment with its strong LOS the close to 40 % values in relative throughput just as for WiMAX. However, in the urban scenario with high RMS delay spread the relative throughput is much lower as the transmitter is producing strong inter-code interference in such channels, visible in SISO as well as in MIMO transmissions.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.