Max Hsdpa User Number and Codes

[ugurkilic]

While there are max 15 hsdpa code , how is max number hsdpa user defined up to 128 ? Thanks for answering .

[subway]

The HSDPA user number is not limited by the standard, nor the number of codes available. But above a certain user number and traffic scenario, you might need to define more control channel signalling resource (HS-SCCH and HS-DPCCH). If I remember correctly, when we seen a lot of MAC failures, that was insufficient HS-SCCH resources on the affected site. Be careful, as in a siuiation like this, the max speed of the site cannot be reached, as the scheduling decisions cannot be signaled fast enough to the UEs. Of course, in this case you will not going to have 15 codes available, as some of the signalling resource will occupy the 15th code as well, not just the 16th.

[ugurkilic]

thanks for answer. But İn ERC cabinet with maxnumhsdpauser parameter , hsdpa user number is defined up to 128 . How can we defined ? Do some users share same codes in one tti ?

[subway]

thanks for answer. But İn ERC cabinet with maxnumhsdpauser parameter , hsdpa user number is defined up to 128 . How can we defined ? Do some users share same codes in one tti ?

What you refer to sounds more like a vendor specific limitations, maybe due to some limitations of the hardware/baseband. In Huawei (and likely other vendors as well), it is also licensed object.

On a more general approach to HSPA: one of the main limitation of code division is that the smaller you partition your code tree, the less efficient it gets (both in terms of signalling and in terms of FEC). Therefor in most commercial implementations code division (or code sharing) is relatively infrequent, and even when they do, the number of user per TTI is kept at 3-4 maximum. The rest is time division multiplexing.

In your case, the 128 user is a HW and/or license limitation. I suggest to check this with your vendor/documentation, as it is not a 3G/HSPA limitation.