A method for wireless communications by a user equipment UE , comprising: identifying a transmit time interval TTI bundle comprising a subset of subframes from a set of subframes for transmitting data on a physical downlink shared channel PDSCH ; and receiving the data on the PDSCH in the subset of subframes. The method of claim 1, wherein the data is in a frame structure of frequency division duplex FDD or time division duplex TDD. The method of claim 1, further comprising receiving signaling indicating the subset of subframes. The method of claim 1, further comprising: identifying another signal configured to transmit in at least one subframe in the subset of subframes; and taking action in response to the identification.
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In particular it was seen to improve VoLTE speech quality. Quite a bit of thinking ahead because we were far away from VoLTE in practice back then. Just a quick recap on how TTI bundling works: Instead of one transmission, TTI bundling transmits 4 different redundancy versions of a packet in the uplink direction, i.
This way, the network can combine the four transmissions and thus cope with more transmission errors. But when I was recently doing some drive testing in the US in very rural areas, I noticed that TTI-bundling actually got activated occasionally. And it was direly needed indeed as the base station sites were so far apart from each other that handovers regularly occurred at an incredibly low signal level of dBm. To set that into context, in urban environments, LTE handovers are done somewhere between and dBm, i.
For details see the specification I linked to in the original post back in On second thought, that makes sense, because measurement reports from the UE inform the eNB about the downlink signal quality. TTI-bundling gets activated when the signal level in the uplink direction gets too low, which is measured by the eNB itself. Also, I noticed that TTI-bundling was used sparingly and was switched-off again pretty quickly.
Back to the VoLTE call. So despite the handovers regularly occurring at very low signal levels, my VoLTE call did not drop over the 45 minutes I had it running. While the VoLTE call staid up, browsing the web at such low signal levels was not possible. Posted on.
LTE TTI Bundling in the Wild
Gugal Emeka Ijere February 20, at 7: In some aspect, you may say this is a kind of wasting resources. Why are the durations of the TTIs all common, or equal? Combined processing of the redundant transmissions over multiple subframes leads to a better probability of detection of the bundlijg block. Should it be always like this i. Maybe that exists as well. Bundllng the basic idea of TTI bundling is to improve performance of VoIP applications at cell edge and therefore it happens only in uplink Hope this helps. A single RLC PDU is transmitted as multiple redundancy versions in consecutive subframes using a single common allocation.
How TTI Bundling for LTE link Budget
The data block in a bundle of TTIs, where the chunk of each bundle up to 4 chunks , is modulated with different redundancy versions within the same HARQ identity. The resource allocation during this operation is restricted to a certain number of PRB and transport block size TBS in order to improve the probability of decoding at lower data rates. The mechanism to transmit same packets four times in one scheduling instance expands the coverage by increasing the uplink transmission reliability with a better success rate gain. In addition, it guarantees that VoLTE packets are transmitted at cell-edge when resources are limited to improve the latency in bad radio conditions. Figure below describes the TTI bundling mechanism and provide comparison with a scheduling mechanism that depends only on RLC segmentation procedures.
TTI Bundling for better HARQ and Latency
LTE TTI BUNDLING PDF