It has been long time since HSDPA and HSUPA came into existence. Untill now we have read and implemented many features related to HSDPA and HSUPA. However following are the basic difference between HSDPA and HSUPA:
- In the downlink, the shared resource is transmission power and the code space, both of which are located in one central node, the NodeB. In the uplink, the shared resource is the amount of allowed uplink interference, which depends on the transmission power of multiple distributed nodes, the UEs.
- The scheduler and the transmission buffers are located in the same node in the downlink, while in the uplink the scheduler is located in the NodeB while the data buffers are distributed in the UEs. Hence, the UEs need to signal buffer status information to the scheduler.
- The WCDMA uplink, also with Enhanced Uplink, is inherently non-orthogonal, and subject to interference between uplink transmissions within the same cell. This is in contrast to the downlink, where different transmitted channels are orthogonal. Fast power control is therefore essential for the uplink to handle the near-far problem. The E-DCH is transmitted with a power offset relative to the power-controlled uplink control channel and by adjusting the maximum allowed power offset, the scheduler can control the E-DCH data rate. This is in contrast to HSDPA, where a (more or less) constant transmission power with rate adaptation is used.
- Soft handover is supported by the E-DCH. Receiving data from a terminal in multiple cells is fundamentally beneficial as it provides diversity, while transmission from multiple cells in case of HSDPA is cumbersome and with questionable benefits as discussed in the previous chapter. Soft handover also implies power control by multiple cells, which is necessary to limit the amount of interference generated in neighbouring cells and to maintain backward compatibility and coexistence with UE not using the E-DCH for data transmission.
- In the downlink, higher-order modulation, which trades power efficiency for bandwidth efficiency, is useful to provide high data rates in some situations, for example when the scheduler has assigned a small number of channelization codes for a transmission but the amount of available transmission power is relatively high. The situation in the uplink is different; there is no need to share channelization codes between users and the channel coding rates are therefore typically lower than for the downlink. Hence, unlike the downlink, higher order modulation is less useful in the uplink macro-cells and therefore not part of the first release of enhanced uplink.
11 comments:
I think this post could have been better titled as Difference between HSPA Release 6, UL and DL.
One question that is bothering me is, why has HOMs been included in later HSPA releases?
Garry
Garry thanks for your comment. In reagrds to HOM, untill Rel6 we only talk about modulation scheme of 16 QAM in DL. The use of higher order modulations (HOMs) such as 64QAM in the downlink and 16QAM in uplink is introduced in Rel 7. These modulation schemes are an attractive complement specially in for multi-antenna techniques (MIMO) in the downlink which again is a part of Rel 7.
Hi Devendra,
Would you please clarify to me why HSUPA does not use Orthognal Channels. Thank you
Hi Sherif
Please see my latest blog for details on orthogonality and non orthogonality
Can you give the lay person a one or two line summary. This makes no sense to me.
Hi all, Can some body show me how HSUPA data rate of 5.76 Mb/s is calculated ?
You can see the HSDPA calculation here and do the same for HSUPA.
Hello there, i am very much confused about this HSDPA and HSUPA, If there is HSUPA implemented on a site , then how we get high download like 6 mbps, whether HSUPA support both downlink and uplink throughput, or they implement HSDPA and HSUPA together on 1 site.
Hello Shaheryar, HSDPA is downlink and can be present without HSUPA (which is uplink). On the other hand if HSUPA is present then HSDPA is present by default.
thank you Mr Zahid
I want to ask one more question.
I am doing drive test for 3G sites in KSA. last time i attented one customer complaint. the customer was getting low throughput or HSDPA because of the number of users increased in that area. The coverage was ok, i-e RSCP and EcNo was neg 70-80 and 10-12 respectively. I submitted the report to operator. and now they are adding new carrier or new frequency to the serving site in the complaint area.
Now the thing i am confused about is that if they are adding new carrier and not increasing the number of E1's (currently the site have 5 E1's). how will it help improving the throughput or HSDPA in the area, when the backbone or or E1's remain the same. How this phenomena work , when we are not adding E1's but adding extra frequency.
Hello again Shaheryar,
I guess the problem may not be the backhaul as that is generally the case. Even though 5 E1's sound less, I suspect the initial thing to try is to make sure the Air interface is not a problem.
2 frequencies means the existing number of users will be distributed in the different cells and may help achieve better data rates. If not, then backhaul needs improvement as well.
Sometimes more users cause interference which is a bigger problem than the data transfer rates and that can bring down the rates of everyone in the cell. You have to factor this into account as well.
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