TABLE OF CONTENTS Continuing efforts exist to improve the demodulation performance of the HS-DSCH (as well as support channels), especially at the cell edge. When a performance requirement is to be set, one needs to define a reference receiver in addition to the channel models, transport channel configuration, modulation scheme, and so forth. For WCDMA, the reference receiver is the well-known RAKE. However, for HSDPA setting the requirements became much more interesting. Naturally, the initial reference receiver for HS-DSCH was taken to be the RAKE. However, it is well known that as the SF decreases, the effects of ISI increases (as was shown earlier in this chapter) and so the RAKE receiver is clearly not the best choice [47 52].
In an effort to improve overall cell throughput and user capacity, other advanced reference receivers were investigated and used to establish performance requirements. We list the advanced receivers keeping the same naming convention as used within the 3GPP specification.
| 3GPP name | Reference receiver | |
|---|---|---|
| Type 0 | = | RAKE |
| Type 1 | = | Diversity receiver (RAKE) |
| Type 2 | = | Equalizer |
| Type 3 | = | Diversity equalizer |
| Type 2i | = | Equalizer with interference awareness |
| Type 3i | = | Diversity equalizer with interference awareness |
| Type M | = | Multiple Input Multiple Output (MIMO) |
For HS-DSCH, the Linear MMSE (LMMSE)-based equalizer was proposed for the reference receiver and is...
